Agreed, for the most part...I only feed my full grown males once every 2 weeks and my adult females every 10 (breeding season is a little different, just like Buzzard said), but it would depend on the size of the prey item and the individual snake (metabolism can differ just like in people, I have some siblings that have been fed the exact same diet since they were babies, and one is twice the size of the other...).
As for your mice, quality food is key. Most aren't cannibalistic if they're getting the right nutrients. My mice and rats get a homemade blend of commercial rodent diet and whole grain cereals (oats, bran flakes, puffed unsweetened rice, etc.) that I found on a rat forum. I've been using it for 3 years with my rats (they are strictly pets) and have been using it for my mice since I started a colony about 6 months ago. So far, so good, for the most part (I've had some cannibalism, mostly first time mothers). Supplementing with a good quality dog food is also a good idea. You'll want to be careful what table scraps you give to mice, as I've read that some things are not good for them (even some of the things I give my rats as treats aren't any good for mice). I stick to things like small pieces of fruit, usually apples, and occasionally some sort of meat, like boiled chicken.
Now, if you start giving them a good diet and the cannibalism continues, it may be time to get rid of the cannibal mouse/mice and start over.