In MY OPINION any one who practices 6 hours a day is eventually gonna suffer some serious burnout. I can't stay on my guitar for more than 1-2 hours a day. This is my little routine when I do pick up my guitar. First I warm up with my scales(metronome). I try to stick with scales I'm trying to learn as opposed to scales I learned years ago. After that I usually play Hotel California (chords only) To get my switching going. Then I usually play mindless stuff to try to stumble onto a cool riff. Songwritings my thing so....
I haven't really tried learning new songs in awhile. It just doesn't appeal to me like it did when I was your age. These days I just try to put together my own stuff. The songs I really thought helped me when I was starting out were Nothing Else Matters to which I owe much of my fingerpicking technique, a few by the Chilipeppers which helped my understanding of melody, Crazy train just because, and Tears in Heaven. Work it out and find what best suits you. Everyone learns different and what works for one won't work for another.