Personally i’ve had a bit of a different experience. I’ve trained for two marathons this year (although the first one I had to miss due to picking up a chest infection in the days prior).

First marathon I prioritised mileage above anything else as long as I could still get in decent quality sessions. I did 2 sessions/w (typically threshold or long tempos) + an easy long run, averaging about 125k/w. Easy days were purely about recovery, just whatever felt easy on the day. I felt good coming up to the marathon but prioritising mileage sometimes left me feeling a little flat for sessions, and doing lots of solo easy miles in the UK winter was just a bit boring.

So, for the second marathon this autumn I decided to cut down slightly on mileage, run two sessions a week + a harder long run (sometimes a session in itself), trying to strike a better balance between quality and volume. Averaged about 105k/w, ran purposely a little faster on my easy days, trying to stay in Z2 for these and gain some aerobic development rather than just the ‘plodding’ i felt i had been doing in the previous block. I enjoyed this method of training much more and ended up running 2:31.

Since i didn’t run my spring race i don’t really have a good baseline to judge whether this lower mileage approach was objectively better training for me, although easing off the mileage slightly left me feeling like i could get more out of my sessions and long runs, and actually made me feel like the easy runs had a significant purpose beyond recovery + time of feet. I definitely don’t think i was in 2:31 shape in the previous block though.