I've worked through a structured FTP building program on Zwift over the winter, and the 1, 5 and 10 minute CP tests fit the Monod curve, while 20 minute under achieves by ~10% (and are lower than my typical results.) Weekly long rides are 2.5 hours in Zone 1-2, and I'm doing the equivalent of 400-500km per month. Longer intervals were 2x10 minutes @95% of FTP.

My feeling is I need to get the long rides to 3hr+ (spring, please hurry), and continue to add time to the longer intervals, but if I listen to myself I'd have fool for a client;-). Given the above, what do you think the limiters likely are?