Rabbits become adults around 6-7 months of age. They change from a juvenile diet to adult diet at that time. That's the main change.
Beyond that, the only changes would be on an individual basis. Some very old rabbits may need their diet tweaked depending on what's going on. For example, if they are less mobile, they may eat less and/or become more gut-sensitive as a result of less exercise.
An older rabbit may not be able to hop up or down to different cage levels as they once could.
My Mocha is about 9 years old (could be older because rescue wasn't sure). I have not made any changes to his diet or cage. He still hops up and down the one level of his cage (though everything he requires is on the floor level).