This year I weaned very early (most about 6 months old) because they were eating me out of house and home.. Prices were good so I shipped most, kept a bull, a steer, and 3 heifers, as well as 3 july/august calves. As a result, I really stretched my fall pasture and haven't needed to start feeding yet. Had I kept the calves the extra 6 weeks I'd have been feeding for 2 or 3 weeks already I'm certain. The cows are in better condition too, I had a couple that were getting a little boney, so they'll pay me back next year with better calves.. you can always hope. This has enabled me to keep more cows.
I do often keep my replacement heifers on the cows a bit longer, a bit more milk doesn't hurt them if it's not dragging the cow down.