is it okay to keep my xbox on 24/7?
 

or at least 12 hrs straight because i sometimes leave it on while i sleep

It shouldn't hurt it as long as it doesn't overheat. It's hard to play with your eyes closed though.

like jive turkey said it should be ok.
but you can set it to auto swich off after 6 houres of inactivity.

it`ll prob shorten the life of your HD.

I leave my work PC on 24/7 and it eats HD`s ..

But i normally buy one`s with 3 year warrenty`s !!