Mmm i dont think its at all a static number. What matters is trimming it down to whats important. If you can keep bringing in new game mechanics, or exploring existing ones in new and interesting contexts, or keeping me engrossed in the story, it can go as long as it wants. Like, Chrono Trigger is considered a pretty short jrpg, because its very condensed for how broad of a scope it has, but boy is it a great game. Mario Odyssey got some criticism for how many moons are in the game, but i loved getting each and every one.