Hi William - you seem to be set fair for your goal, which as others have said, is admirable at age 65. As others have also said, as the years go by, one needs to pay more attention to the recovery aspect - (I'm 55 and need more recovery between harder sessions than previously). However, in your favour is the fact you don't have multiple marathon campaigns, and therefore have "fresher" legs. Your 3:02 20 miler suggests sub 4 marathon is nailed on provided you don't do anything daft now. Don't know what your schedule says, but IMO you don't need to do anything further than half distance now, and leave 3 weeks after that to taper well - FB & "Bluebirds over" are spot on - the taper is very important to ensure you are rested and fresh. Good luck - is it VLM you are doing?