Party enters Keep on the Borderlands and does pretty well. After several days of hard adventuring characters A and B have bumped and need training while C, D, and E haven't yet. Party goes back to the town to restock; A and B stay there to train up and are replaced by new recruits F and G. Party goes back in; a few days later C needs training, D is dead, and E (who judging by its slow advancement must be a Paladin!) is still 1st level. Party goes back to town again; A and B are still training, C joins them, new recruits H and I are taken in, and back into the field they go.Then you are the anomaly IME, not the norm.
Why? You can adventure without leveling, so if you are pulling a PC out of the adventure to level you are sort of metagaming IMO because their only reason to train is to gain a new level...
Lather rinse repeat; and thus is troupe play born.
If someone can't adventure right now because she's busy training I'd say that's pertinent to the story. The party have a choice: recruit a replacement and carry on, or wait for her to finish training and thus maybe give the dungeon a few weeks to restock itself and prepare defenses.So, like I said, IME we only pulled PCs and introduced new ones if it was pertinent to the story.