How long can a rooster keep breeding?

A rooster only needs to breed the hen one time for her to be able to lay fertile eggs for 2 or 3 weeks. Also The passage of the sperm up the oviduct is rather slow so it may be a few days after the first encounter before the egg is viable. If you are introducing a new rooster to the flock and there are no other males give the birds some time before collecting eggs for incubation. 10 days should ensure all the eggs collected are viable.