theres not really a certain time it just depends how much you use it each day. I know I saw a post about how long you can play on each jtag so it won't RROD I think it's in the Jtag Discussion.

I agree with 1-2 hrs, mine use to freeze/ rrod after about 2hrs, Then i took it out of the case and use it w a huge desk fan on top of it

it doesnt really have a time as long as u dont bang away at it for about 7hrs a day

I don't recommend leaving it on longer then you need too. Don't use it like a normal xbox, only have it on if you need to infect yourself or want to play a modded game. You should have it off when ever you don't really need it. This will give it a longer life, since most jtags are fixed RR consoles.

i got a 80mm blue led fan on mine and a 12v fan mod and i have had it for about a month and it runs great