things start changing in your 40s… This season I did a couple high volume blocks (8-12 hours/week) but with fewer intervals and got faster versus doing TR SSB-1 HV and then SSB-2 MV with mods.
Sometimes fresher is faster, particularly if you benefit from more recovery (at any age). You won’t know if you don’t try, so experiment and figure out what works! I’m definitely sold on 8-12 hours/week to build a strong base of aerobic fitness, the question then becomes how you fill those hours and organize the year.