IME training was almost universally used. Different communities, I guess.
I guess so, though honestly, I'm surprised to hear this. The fact that different classes leveled at different rates pretty much assured that at the point one character needed training, the others would not. This would have necessitated retiring a character for several weeks from the campaign. Weeks of game time is an eternity of real time. In my experience, each session averages about a day of game time. Putting a character in down time any time most other characters are not in down time is for many campaigns the same as retiring the character. Everyone has to be willing to retire their characters to down time at the same time. And as a practical matter, this means that the variable length training doesn't really mean anything for small groups.
The training imposed also huge burdens on the style of game you could play. Training makes sense as a rule only if you have a large cast of rotating adventurers, and possibly a large cast of rotating players, and large dungeon containing mostly passive and reactive foes nearby to a large metropolitan area. In other words, much of the 1e AD&D DMG and the rules and advice therein can only be understood in the light of Gygax's original Greyhawk campaign, and as house rules evolved to handle the particulars of that situation. If that is your situation, Gygax will seem sageous and prescient - because this is the distilled wisdom of actual play experience. Removed from that situation, Gygax's advice is a lot less applicable.
If you are playing a wilderness game, you pretty much have to assume no leveling the whole time the party is in the wilderness because there is no one around to provide training.
If you are playing a story based game, the plot must routinely stall to give players time to train.
If you have active or proactive foes, they must routinely cease their machinations in order to give the PCs time to become stronger in peace.
Even Gygax's own modules show that outside of the Greyhawk campaign structure, training was generally waived and not expected. The GDQ series gives no real expectation of time off for training, and is designed such that the characters need to level up as they progress and will receive the XP to do so. If XP is being lost through lack of training, the early 'adventure path' just doesn't work.
That's almost an apples-and-oranges comparison, as not that many 1e games ever got to 15th level (the system kind of petered out around 10th-12th). 3e was designed to go to 20...
Whether it was intended or not, I never perceived 3e as demanding 20th level be reached. Rather, I believe that 3e provides structure for the game to continue up to 20th level should it go there based on the experience many 1e DM's had that after 10th-12th level, they were pretty much on their own regarding providing reasonable challenges to players. But I never perceived the fact that 3e could go to 20th level as being a requirement that it could go to 20th level, any more than I perceived the fact that the XP tables for classes in 1e reaching 18th-24th level meant that it was an expectation that games would obtain those levels.
, and a 15th-level 3e type is, relative to the system, about the same as about an 8th or 9th level in 1e. But you're right about the monsters, for the most part, at least by RAW.
That said, you're speaking to a tangential point to what's in play here: the difference between 1st and 10th levels in 1e vs. the same difference in 3e-4e. 1st-level in both 1e and 3e is reasonably close to the same thing, but the scaling curve in 1e is simply not as steep
I disagree. First, 1st level in 1e vs. 1st level in 3e is not nearly the same thing. In 1e, the first two levels where generally deemed to lie outside the games 'sweet spot' (usually sited as levels 3-8). This was because 1e 1st level characters were generally pretty pathetic, and baring cheating or lucky rolls, where typically inferior to say hobgoblins. This is especially true prior to the weapon specialization rules and cavaliers appearing to turn low level fighter types in to weapons of mass destruction. In 3e 1st level characters were consciously front loaded with more spells, more abilities, good ability scores by default, and maximum hit points in order to ensure that they could do more than 'kill rats in the basement'. The 3e 1st level characters are further up on the curve. However, the scaling curve in 1e is even steeper than 3e. While the 1e 1st level fighter is challenged by a single hobgoblin, his 10th level counterpart can probably take on 200 solo, and is facing things like old dragons, frost giants, and balrogs - things that for the most part have been moved further up the slope in 3e. In 1e, leveling up starts out fast and then slows. The exponential table means you'll catch up - your whole career from 1st-9th is the same as your companions grind from 11th-12th. In 3e, the linear advancement table and the constant rate of advancement across all levels means you're always stuck well behind.
and if anything you have it backward: in 1e a 10th-level fighter was relatively weaker in comparison to a 1st-level than she would be in 3e;
I don't see that at all except perhaps in the case of a fighter with greater than 18/50 strength (because of the huge outscaling that starts happening at that point 18/00ish strength is game breaking). By your own assessment, 1e 10th = 3e 15th. The low level 3e fighter has far more positive modifiers, with ability bonuses starting at 12 and the ability to acquire feats - its relatively easy for a 3e fighter to have a +6 to hit bonus and be doing 2d6+6 damage - which is far beyond the average 1e fighter absolutely and relatively. And the fighter will likely still have 'room' for bonuses to AC and hit points. The 1e 1st level character has nothing go for it and will behind the 3e power curve until crossing it (in a relative sense only) sometime in the mid-levels and then taking off. The UA somewhat evens it up in the case of some classes - 3e tends to balance with the UA classes more than the original ones - but low level rogues, clerics, and wizards are still much weaker than their 3e counter parts both relatively and absolutely.