Longer rides for me are 2.5 hours with 3 hours being the maximum. I rather go to Fiesta Island and ride a fast 20k time trial or do structured training than grind for hours.
I like to ride high z2 low z3 constant power with more emphasis on z3 for longer endurance rides. I like to go fast and z2 power just does not have enough speed for my taste and z1 is a waste of time other than for warmup and cool down. And if I am feeling good, I will through in some z4 threshold efforts to spice things up.
I try to hold constant power per a schedule and I do not ride to a speed unless I am doing team time trial with a partner where holding speed for a given wind and terrain situation is important.
I like to negative split my endurance rides and finish with more power than I start with and generally ride solo or with a training partner.