Every coach that I have used seems to have their own protocol for adding endurance in a periodized training program to support a goal. Currently, I am not on any program other than stay fit and healthy and be ready for the start of next seasons periodization.
I like a 2.5 hour endurance ride that skewed toward tempo and do that a couple of times per week. My goal in those rides are very little z1 and coasting. However, during programmatic training, I do as I am told.
I am retired and can do what I please. I do not find long rides that appealing and prefer going to the track and working out with a coach and others in a structured workout for 3 hours. Due to the pandemic, that is not available.