Theory: Ben has a history of hitting the Omnitrix too hard, which sets the Limiter to random. It’s entirely possible that it got stuck on a longer time limit.

True, but he didn’t (sorta) learn this until Omniverse. Btw, I wouldn’t wanna try and get a good night sleep at the bottom of a lake with a random time limit ranging from seconds to hours xX

Ben’s not too bright. Plus, not knowing about something doesn’t necessarily invalidate it.

True, but I doubt that it was the case xD