We have 38 large breed chickens (33 layers, 5 roos, last count) They free range all day. They have access to 12 acres, but choose to graze & forage on only an acre or two. We fill a thirty pound feeder with a mix of corn, soybean meal, wheat, oats, grit, diatomaceous earth, & a mineral "base" mix, about once a week since the grass came up. They have access to it all day, but they much prefer the bugs and grass. During the winter, they empty the same feeder every 2-4 days, depending on the temperature outside. We get approximately 24 eggs every day, even in winter, with exceptions during extreme weather. During the winter we did provide them with a few extra hours of light-timer switched it on from 4 am to 8 am, when it got light out, dark was here by 5-6 pm.
So, yes, to keep them healthy and laying well, you do need to provide a balanced feed mix, even in summer, but, you WONT spend a significant amount of time or money feeding them.
Beware, however, that you will be very likely sucked into spending hours watching "chicken TV" during nightly chores and will be shocked at the amount of time that escapes you. Chickens are very distracting....