Something else though, which you don't mention, is why are you going to deposit and play? Is it for some recreation or are you aiming to make a bit of money to spend on something specific. Is it even that you are aiming to make a living at it?
If it's either the 2nd or 3rd, then you won't make much money, even playing 5 to 8 hours. Do you have a track record playing offline, and if so, at what stakes and with what success?
I've been reading Johnathon Little's volume 2 book, which has a superb section on going pro, making a living, the stakes you should be playing at (the 100BB, 50BB etc above is spot on). It also talks about how going pro should not risk your life, your commitments (family? Mortgage?) and talks about taking into account your outgoings and how fast you can assume your bank roll can grow.
It sounds very tempting and "easy" to play pro and make loads of money at something which isn't a real job. But playing full time is hard work, it is a real job, and 5 to 8 hours solid is mentally tiring. Don't for a second think it is easy!
Personally, I play for recreation as I love playing, and make some money on the side. I can win at higher stake SNG's but it takes such concentration I find its actually not worth it. Im now playing $15 SNGs as I can win without trying very hard, make some money, and enjoy it at the same time. I don't need to look at poker as a job, I've just started my own business with a partner which should make far more money than I ever will playing poker.
If your pretty good and focused you can make good money at poker, but it is a full time job!!!