Well back when I first found out about the tourney scene and started going, I played daily for hours. Against CPUs and wifi (I do not recommend this at all). I then got lots of practice at tournaments and smashfests playing for hours with other people. I wasn't too active before I retired actually. Once I got that top skill level, I was able to be less intense in terms of practice, because I had such a handle on the game. So practice as much as you want/feel like you should and test the results in a tournament. If you feel like you need more work, step up the practice.
I actually got 17th at my first tournament out of 80+ back in June of 08. I left after I lost in winners (didn't comprehend double elimination since I was a noob lol). I got 17th like 2 more times, then 9th twice and then in November of 08, I got 4th beating some top players in TX. Before that, I got close so I knew I was getting close up there. Once I hit that 4th, I knew I was good but not good enough. During 09, I took over TX and knew I was the best for a while. So late 08/early 09 is when I felt like I was at a higher skill level.