Denny said it all, but I'll add my recent experience. This winter I moved from fly-sparging in an igloo cooler in the garage to batch-sparging in an 8-gallon pot in the kitchen (the garage was getting cold here in New England). I have since settled into a very simple 4-gallon mash, 4-gallon batch sparge with a typical 10 to 11 pound grain bill. This gives me about 6.5 gallons of preboil wort, nice-n-easy. If necessary, it is pretty easy to either sparge a bit less or a bit more to hit your target volume and/or gravity. That's one of the beauties of batch sparging in general - keeping things simple.