If you are considering an IVA, then you would discuss your retirement with your IP at the beginning. When you enter an IVA you are agreeing to make the payments, if there is any reason why you think you can't do this, then you must tell your IP.
IVAs should not be timed to extend past retirement. An IVA does not have to run over five years, I have several cases for older clients which are over three or four years, the end to coincide with their retirement.
Are you taking early retirement which could not have been forseen at the outset?