In college I practiced 9 hours a day...proof that merely practicing does not get your there.
My high school band director had a sign posted that stated "Practice makes Permanent."
These days I practice organ about 1 to 2 hours/day, off on Friday.
One time a guitarist friend and I jammed for about 6 hours. We'd play a tune, and then we'd say we were tired, and then we'd start playing another tune, and then we'd wake up, then, we'd stop and get tired, and this went on for 6 hours.