If a field adventurer can go from 1-10 (any edition) in less than 2 game-world years, a mercenary can certainly do it in 10 years, or 15...particularly if there's lots of little wars and battles to get involved in and paid to fight in.
Time isn't the only or even necessarily major constraint. I agree that if you can level up in two years or less, that obviously you can level up in 10 or 20. But this ignores the complexity of the problem. In earlier editions, a mercenary might expect to fight in a hundred battles before going from 1st to 2nd level. Even in third edition it would require a very great many such battles (though less by an order of magnitude). How often do battles happen, and even if only a fraction of the participants die, how long can a society continue to support such slaughter? At medieval scale, a society might could support one battle a year, or maybe two or three in a particularly intense year and a mercenary might move from country to country and always find a battle each season, but even so would need to be a centunarion to reach level 2 in this manner. As logistics improves, the pace of battles can increase in later historical periods, but typically the wars also become shorter and more spread out.
The intensity of the adventuring life is hard to replicate with anything else, whether we are awarding XP for foes defeated or awarding XP also for treasure earned.
This one's edition-dependent; in 1e all you had to do was find treasure to earn x.p. - you could in theory get to decent level and never kill a thing.
Oh sure, but as long as we are quibbling over the details, lets really dig up the details. If you assume the treasure table, number appearing, percentage in lair, and the encounter tables hold, you'll find that stealing stuff by stealth to gain levels is not particularly easier of a job than stealing stuff by violent force. Most monsters will have on average startlingly little treasure if you are used to adventure paths like G1-3 as your standard. It's only in the dungeon, that treasure is relatively common. The mercenary life affords very little oppurtunity to enrich yourself if you are following the rules.
that all battles are to the death. Remember, x.p. are earned for defeating foes, whether said defeat is by surrender, subdual, changing sides, or whatever - it all counts. Thus, it's entirely possible to fight the same foe more than once over time.
I don't need to assume this. I only have to assume that a reasonable percentage of combats end in death, and that XP is only awarded in full if there is truly high stakes. If you award full XP for to combatants fighting each other but neither having lethal intent nor their being any real stake in the outcome, then obviously it will be much easier to obtain high level but don't be surprised if your PC's gain most of their XP through staging mock fights with each other.
that the only foes are other people. There's lots of monsters out there that are just as good as humans (if not better) at reproducing;
I don't need to assume this either. I only need assume that monsters represent at least as much threat to the human ecology as other humans do. If dragons mostly eat sheep, and refrain from killing the shepherds that would protect them, and if ogres have no taste for human flesh, and so forth, then it might help matters to replace human foes with monsters. But otherwise, not so much.
- that the only way to earn x.p. is by combat. While in some editions by RAW this is true, it's not a big jump to give x.p. for research, invention, and other successful pursuit of activities related to one's class that don't involve combat.
And I address this already. If your answer to how much XP is gained per day of research is 10 X Level, then yes, it is certainly reasonable that most people in the game world will be high level. But you must accept the consequences of that. Most people will be high level, since it only takes a few days of each year in training to gain a level, most people will be 10th level or higher and PC's starting at 1st level really will be schlubs. Likewise, don't be surprised if PC's see training as an efficient way to gain a large portion of their XP. On the other hand, if you assume that each day of training gains you 1 XP, then under the 1e module even levels with 600 year lives might have trouble reaching name level before becoming venerable and frail if they devote themselves to the craft. Even under the 3e module, the same assumption might get you to 4th level in 20 years pursuing a craft.
All I'm saying is that if you assume that training suffices according to some house rule, you have to accept the consequences of that. One consequence will be that the PC's are schlubs until such time as they increase in level beyond that normally obtained by training. You've departed very very far from the world of 0th level men-at-arms and 1st level characters are rare heroes.
No. There are more than that.
I think you misunderstand me. You seem to think that I'm saying that there are only 20 or 30 times as many dungeons in the whole world as the PC's visit. However, often as not in my games PC's will obtain high level just on the basis of the dungeons in their 'back yard' and its assumed every little region is dense enough with dungeons to provide a rich adventuring life to anyone in that region. The question was not, "Are there 100 dungeons in your world?", but rather, "Are there 20-30 dungeons in every hill and valley?"
They come from about a quarter-million years of civilizations rising and falling and rising again; from monsters gathering hoards then dying alone; from artificers messing with magic and creating works of art that end up forgotten in a mathom house; from previous adventurers' strongholds now abandoned; from Necromancers achieving their career goal of Lich-hood; and from a thousand other sources not mentioned...
Yes, yes, yes, that's assumed.
Why the heck not? If I'm supposed to be running the show, why not hire my own gang of bashers to keep the place in one piece?
Because its really really inefficient. Just as the adventurer hordes as much XP and treasure for himself as he can so as to be able to overcome the challenges he faces, the post-adventurer lord hordes as much XP and treasure for his retainers as he can. It does him no good if random adventuring companies owing him no fealty and of alignments perhaps conflicting with his own deck themselves out in magic items and level themselves up in to the realms of compotence and self-sufficiency. The post-adventurer lord seeks to ensure that anyone who is anybody is also somebody who works for him and whose loyalty he can command. Because, if he doesn't, then some other Lord who has been doing the same takes his gold and hires the mercenaries out from under him (you having less gold to spend because most of its ended up in the pockets of random hirelings), and comes at you with his army of veterens and his company of high level followers while your own followers are green and poorly equipped. And then that other Lord takes what you have for his own.
If they occasionally find a dungeon it means I don't have to pay 'em, they can keep what they loot.
I fail to see how you benefit at all from that compared to having your own retainers, henchmen, minions, and followers take the loot and the XP.
Also, when you ain't got the fire in your belly any more you retire and let others do it - that doesn't necessarily make you stupid or lazy, it may only show you've moved on from (to use a sports analogy) playing to coaching.
Ok, fine. Under your analogy all your efforts end up going to training a team that doesn't play for you. The good coach makes sure its his team that recieves the primary benefit of his experience.
