FoxWander
Adventurer
I'd have to agree with Blue- it takes real XP to advance in a PC class. If your just living the average, everyday peasant (by "peasant" I simply mean "non-adventuring folk") life- you're limited to NPC classes. This is really the model most D&D worlds are based on whether they know it or not. There just isn't enough day in and day out excitement in the peasant lifestyle to justify levels in a PC class. Sure a rough year of goblin/orc raids might get the town defenders a level of fighter, but that should be about the limit. Almost every other example of the non-adventuring lifestyle can be handle, and quite well, by some level or combination of NPC class levels.
For a really good explanation of why this is so, and a very good guide to what level a peasant of a given age should be, see Sean Reynold's A theory about peasants. Using his system it's very easy to figure out NPC levels that should feel realistic. It's also quite easy to justify levels higher than that by increasing the hardships a given peasant has survived. But, realistically, without the "daily" trials and terrors that PCs must face (or a concerted effort by an NPC to specialize in some area- thus taking a PC class), levels in PC classes don't really make since.
For a really good explanation of why this is so, and a very good guide to what level a peasant of a given age should be, see Sean Reynold's A theory about peasants. Using his system it's very easy to figure out NPC levels that should feel realistic. It's also quite easy to justify levels higher than that by increasing the hardships a given peasant has survived. But, realistically, without the "daily" trials and terrors that PCs must face (or a concerted effort by an NPC to specialize in some area- thus taking a PC class), levels in PC classes don't really make since.