I play my bass almost everyday and practice for about 1-2 hours when I'm alone. When I goto my drummers hosue tohugh, we'll jam any where between 4-7 hours (with a few breaks[drinks,bathroom,etc.])
I feel I'm progressing at a good speed, and that I'm starting to develop my personal style of playing.
And when I don't play my bass for 1-3 days, my fingers get very antzy and I feel sorta guilty, cuz I don't want to lose my touch(or my callouses)
The only thing I can sday that would be(hopefully) universal is, practice enough that you feel it's making oyu improve oyur playing, but not to the pount that you feel it's too much in too short a time
Whever and whoever you are, ROCK ON!!
