I practice 2 hours a day. The first hour I will work on my guitar skills or theory, then the other hour is for jamming or learning songs.

Like hunter said, top knotch guitar players have praticed for years 5 or 6 hours a day. I remember reading somewhere that Steve Vai practiced up to 9 or 11 hours at some point in his life :o

Just remember to have fun. If you can have fun 3 hours a day, good for you. If its only 30 minutes, good for you :)