Well, the Dersians and Prospitians have existed there for all eternity, but before John showed up, Dersians and Prospitians were two chess kings chasing each other around a 3x3 board. And I think they've only existed there for all eternity for a few hours, the Medium having been created ex nihilo when John connected, complete with history. Just like the planets. And I don't think the troll adventure took long enough for them to age noticeably, even if the epic boss battle with Demonhead Black Kingpin did take about as long as everything before it. So, yeah, I don't see any evidence that they WOULDN'T age, although there isn't anything against that either.
I think that between Spidermom and Gl'bgolyb, the trolls are going to have quite a challenge with their game, despite several of them starting with the best possible weapons or strong enough to punch the head off a colossus. And I'm kind of worried about the normal people. Well, actually, most of them started when the game was still young and none of the really bad things had been prototyped yet. Karkat and Terezi had already been beating crab imps, dragon imps and centaur imps for a while before the giant statue frog imps appeared. And then had a chance to level grind on those before spider imps showed up. And I think Feferi was like the second to last player to enter.