'Course, you don't need to or have to feed them at all, and I've never killed a deer at or even right near a feeder. But my buddies have and it can help to keep them in the general area. I've killed quite a few within 200-250 yards of the feeders in past years. I haven't used a feeder in several years, but I'm contemplating putting out some feed this year in some archery-only areas, since I finally have a 4-wheeler to make deliveries instead of the sweat of my brow. I *do* put out some "apple salt blocks" every year, in multiple locations.
I think that *most* people who feed / bait them wait until the cold drives them to really crave the fats in the feed, which is not until November or December in the South, and not until October in the north. It's certainly much more productive of a draw to feed them when it's cold and barren with ice and snow around than in September or early October. But still, even with plenty of natural food area, during the early season, if they find your feed, some of them will still come back to it occasionally since it's forest candy to them, not a bitter acorn.
If you don't know, don't ever hunt over a feeder. Always back off a bit, in at least a 75 yard radius, give or take, and look for pathways going to the feeder. Big bucks will never go to a feeder during the day. But he *might* just be standing a little ways off from a doe during the rut, so if the doe is at the feeder, and you're 50-100 yards out, then you might just hit paydirt.