I can't stay in zone 2 unless I'm riding with others in a paceline. I don't worry about it. I do try to do some rides at what to me is low effort. Sometimes I can manage to get a majority of my time in zone 3. But that takes some effort on my part to keep from attacking a hill.

If you only have a limited time to ride, then don't worry about it. Do what makes you feel good about the ride. Are you riding 3 or more times per week?