For me I would think it would depend upon what you want to achieve, what are your goals, who are you playing and what is their level.
For me, I started late @ 18, so I was way behind in years played as compared to McCready, Cole, Keith Thompson, Ernesto and the like, the child proteges, so I had to really practice.
I practice 7 hrs. a day and then went out at night to match up. So I probably practiced anywhere from 14 - 20 hrs. for every 1 hr of matching up. I practiced all disciplines of pool: straight pool, banks, one pocket, and nine ball.
I got lucky, for as Luther Lassiter stated; "if you want to get good at pool, practice on a 5 x 10"! That was always my table of choice.
Other than that I can not add to the already good advise the posters have offered up! Good Luck! Whitey