Unless they are spilling the food, they really do need to eat as much as they are eating.I have pvc food dispensers and they have access to the food all day. It has the layer crumbles. We want to eliminate that so we can monitor how much their eating.
Chickens will typically not over-eat when they have a complete feed (like your layer pellets.) They usually eat the right amount to stay in good health and produce eggs, without getting too fat.
If you try to limit their feed, they will typically not lay as many eggs, and at some point they get skinny and unhealthy.
So I would try to make sure they are not spilling (wasting) the food, and that no wild animals are eating it (mice, rats, squirrels, wild birds, etc.) But I would not try to limit how much the chickens themselves eat.
I would expect 50 pounds of feed to last about a month for 6 chickens. If you are going through it a lot faster than that, I suggest you double-check whether it's getting spilled or whether other creatures are eating it too. If you are using a lot less feed than that, it would mean they are still getting a lot of their nutrition from the compost pile and other stuff available to them.