Your 4000 CI pack is too big if you're not carrying 4000 CI worth of stuff.

I go up to about 4-5 days tops with an 1800ci "daypack" with my sleeping pad strapped on the back. though. Technically now I'm using a 50 litre (3200 CI) pack most of the time, with my sleeping pad as the frame - basically a tube on the inside that everything stuffs inside for most three season lightweight backpacking, trips up to about 7-8 days. I'm betting I'd max out at about 10 days food in that pack, with the gear I carry.

In winter I carry an enormous 70 litre jobby.

So the answer is "it depends". Your pack size shouldn't matter as much as how much weight you are carrying.