That's pretty much all I ever get, 5-6 hours. That's what happens when you work 12 hours a day.
I usually feel fine for it though, anything less than 5 hours and I start feeling like complete shit though...
I find the same thing with front squats. Love the way they hit my core and knees too but they're a right old pain on the shoulder where you rest it.
--------------------------------------------------------------------------
Defeat is the stepping stone to victory.