Celebrim
Legend
Good downtime systems. E.g. both Runequest and Ars Magica have them. Imho, it's a good sign if you don't want to spend all of your time adventuring.
This is a tangent, and I'm not jumping you, it's just I hear this sort of thing all the time and I don't understand it.
It also eliminates the really odd D&D effect of getting from level 1 to 30 in a month of game time.
I hear this a lot but have never experienced it. The odd thing is that I hear it most from people who also complain that D&D has a 15 minute adventuring day. Well, if that's the case, shouldn't it take at least a week or two to go from level X to level X+1? Because either D&D has a 15 minute adventuring day where you can only get in one or maybe two encounters per game day before you are encouraged by the system to rest up, or else it takes a game week or even two to level up but it can't be both unless you're way off in house rule land.
My experience with D&D has always been, whatever the version number on the system, that the 'hero's journey' takes about a year with level up every game week or three depending on the distances involved in making the hero's journey. This to me corresponds well with the expectations of literature.
Other styles of campaigns will have different, usually slower, rates of leveling up. I've been reading 'The Deed of Paksennarion' lately, and it begins with a gritty mercenary campaign where the character gains about one level per year. Most of the time is spent in march or in camp. We've now changed about 1/3rd of the way into the book to a 'Hero's Journey' style campaign, and levelling up seems to have speed up significantly so that by the end of this year (of the book) I strongly suspect the protagonist will be raised to name level.
If you are doing an 'Hero's Journey'/'Adventure Path' style campaign, the problem isn't that there aren't worthwhile things to do other than adventure, it's that you are in the middle of adventure and you don't have time. It's always going to be more worth while to save the world first and then take a vacation than take a vacation and fail to save the world. I'm stuck with this problem myself, in that there are lots of 'down time' options for the PC's (crafting, training, vacation, spell research, etc.) with tangible benefits, but the world wouldn't leave them alone to let them do them.
My guess is not so much that Runequest and Ars Magica have far superior options to D&D for doing things in the down time, as at least 1e through 3e have given the players plenty of options in that regard, so much as Ars Magica and Runequest have started with or come to have different default assumptions about what the story is like.
In 1e for example, I always found that after the 'hero's journey' phase of the story, leveling up came to a crawl in game time, not only because the amount of XP to go from level 12 to 13 was so great, but because the game changed its assumptions implicitly and explicitly as to what the game was about. The hero had arrived at his destination, and transitioned from hero to lord, and thereafter in the game political themes dominated and there was a lot of down time as the events of the world moved at their own pace and the PC's turned to the affairs of maintaining their strongholds.