Its more than 4 years since my last post in this thread, since when I have run around 8 half marathons a year, the London Marathon, and a variety of other races at 10k, 10 mile and 15 mile distances.
In all that time I have followed the recommendation I made in November 2008. I use my aspired time as the 'Recent Race Time' and it has given me a good plan to work to. Its what i am currently using in training for the London Marathon again in April and the 2 Half Marathons between now and then.
Frankly I don't think age makes any difference with the training as you are working to a time. I still score new PBs every so often, and certainly can't run any faster than 7:10 pace even downhill, but that's my age and it doesn't affect the legitimacy of the SmartCoach training plans so long as, as I said last time, you listen to your body.