For a bunch of reasons, my strength and endurance have been in a 4 year decline, despite a more than adequate number of hours in the saddle. This included a frustrating DNF at an event I traveled 1000 miles to ride last year.
My FTP appears to be down 15% from the last professional test. Part of that is the fact I have gone to unmeasured (distance, speed, cadence, power) rides both on the road and on the trainer, despite having the tools. I think I have convinced myself that I'm going harder than I am.
So, for the next three months, I'm doing structured work on the smart trainer, six days a week, and keeping track. At 61, I'm willing to suffer for a bit on the trainer, if it brings the pleasure of stronger riding come spring.