I've never done a Hanson's program but I don't focus on 20 milers anymore in my training. My last marathon was 2:58 and my longest run was 17. I run higher mileage throughout the week and keep the 'long run' on the shorter side. The norm is to keep my long run under 20% of my mpw.
I have run other sub 3 hours doing the conventional '4 20 milers' type programs but if I can run the same times with a shorter run I will. Not that I'm afraid of 20 milers but I don't see the sense in doing them, at least multiple times, if one is running 70 - 80 mpw.
Better to keep your mileage short and run fast, which is what the Hanson's plan focuses on as I understand it.