I'm revising for over 2.5 hours a day (usually 3.5) and have been since a week into A2...I don't wanna risk forgetting everything, and I'm focusing especially on content I found especially hard last year. I'm also making notes all through AS again.
I'm not even doing the most work in my year - one of my friends works past midnight from 16:00 every day (I think she's nuts) and my other friend gets into school from 7:00 AM and stays, studying, until 17:00 Mon-Fri.
So, I'd say no. Not too early at all.