What happens after 100 hours gameplay in ruby?

Answer 1

Nothing, usually. You might, however, come across something called The Berry Glitch that only happens in Ruby and Sapphire. Your berries never grow, and your internal clock freezes. The internal battery will die out shortly after. It will not affect your save file, though.

If maximum time is what you were concerned about, don't worry about it. Maximum time can go up to 999 hours and 59 minutes.