My BOB is also my Search and Rescue 'Ready Pack' as they serve a similar purpose. I put mine together with enough food to last 2 days comfortably assuming a lot of activity. Considering how long the body can go without food I could last a lot longer if I had to using those two days to travel, build shelter, gather wood, assemble signal fires, or whatever while I was fed.

As far as sleeping bags so I'd say it depends on the weather. Where I'm at in Alberta, my BOB has a sleeping bag. I put it in a O.R. stuff sack bigger than the original to save the loft (TNF recommends storing it in the original bag so the Loft should be fine). Come summer I'll likely only take my AMK 2.0 bivy.

A good shelter can make all the difference. The shelter you learn to build at the Boreal institute can keep you comfy at 40 below or worse with a 20 degree (-7 C) sleeping bag (and a good fire). They call it a Supershelter. It incorporates some pretty simple materials...including a space blanket. The way the Supershelter is built, you could heat it very easily with just a candle if you had to.