I ran 3:43 when I was 65. Unfortunately, I had an injury that kept my mileage down I was aiming for sub 3:20.. But here goes:
One long run each week working up to 22 miles - I believe in the long run and always did 10- 12.
One marathon paced run working up to about 12-15 miles a week
One speed workout each week (you can skip some but not too many), either 800 or 1600 repeats, whatever you can do. Try to work up to 6 or 4 with an easy recovery. I always hated doing mile repeats.
Easy 5,7, miles on the other days.
That is about 50-55 miles per week. I like to work up to around 70 mpw toward the end if you can. Do it by doing doubles. Modify any way you want to, but higher mileage pays benefits - faster times - if you could work up to 80 or 90 for a last few weeks, great. . But you know that.
I have never believed that aging required longer recovery time. I always thought it was a myth that we all bought into like the seven day training schedule or the "don't increase your mileage more than ten percent a week" Your body can't tell time or recognize percentages. I suppose if I was running 100+ mile weeks when I was in my sixties, I'd feel differently.
But that is just me. Good luck.
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