I find I’m actually better if I even miss some of the endurance works. I’m 37 but find a VERY easy rest/recovery week works best for me
Usually 2-3 days off or super easy (depending on fatigue) and then I use the rest of the week for testing. (often a swim/ run TT, but also a FTP test as I do the 20min format and I find that’s better done with a bit more recovery before/after compared to the ramp)
I’m 23 and recover pretty quickly, so a whole week usually leaves me super flat and struggling with the first couple of hard workouts. Also maintain a fairly high TSS generally, which I think has a bearing on what counts as “recovery” relative to loading periods.