Not sure. My willpower is limited, so sometimes I totally ignore my "routine" and sleep in to noon. (I did today.) It's 2:30AM here now, so obviously I am not going to be waking up at 4AM today :)
I am sticking with the 4am thing for two reasons. One, I like to ride my bike around 5:30 or 6-ish in the morning because nobody is out running on the trail I like at that time. (Runners are very dangerous.) If I go in the afternoon, I have to skip the trail and use surface streets instead, and a 14 mile ride takes an hour and a half. In the morning, I can do 25 miles in that time. So more exercise, less cars, and better scenery is one incentive to get up.
Another thing is that I have all my meals delivered via some service that does that, and they come at around 4:30 or 5. So I have to get out of bed anyway.
In the end, there is an infinite number of things to do that take time, but only a finite number of hours in a day. So if you are intent on setting a routine, you aren't going to be able to do everything you want. If you are flexible, though, then you might be able to.
For me, I identified, "I am tired after work" and moved things that don't require being non-tired (watching TV and sleeping) to after work. Then I moved everything else to before.