if you're into rock and metal can i recommend you try some early metallica, any maiden, some beatles and some classic rock riffs. metallica's early stuff uses a lot of good, well structured riffs that'll teach you a hell of a lot, as with maiden (though maiden use some good, worth learning lead guitar and chord patterns), beatles songs have a lot of good chords to learn and the rock riffs are just cool :D

i used to practice for 10 hours a day. dont think it did anything for me good or bad. when i got older it was 3 hours, now its probably less than 1 due to work and kids. i really dont have time for that now but i tell my students to go for atleast 30 mins a day, pushing it further if you desperately want to learn something.