My FTP has gone up 20 watts since December or whenever I started, but I still feel the weekend 3-5 hour fast group ride is key. I try to do these on Sunday when weather permits. Helps dial in my nutrition, pace, and handling. I’ll do the same when it is closer to xc season for me.
The TR plans are great, we are all time crunched, but gosh, the weekend long rides I feel do so much.