It seems like it would be tough to make sure you're getting the 'same' workout in though, even over several days. Or is that just me? Sometimes we'll work on transitions, other days might be more on suppleness, others might be mostly 'picky' things like stopping straight and lateral work, and still others might be trotting on an actual circle rather than weird oblong shapes. Do most people have a more set routine? I ride my guy about an hour at a time six days a week.
I don't think it's about making the workout the exact same every time, but about knowing the intensity of the work.
For example, the day you work on transitions, are you doing mostly walk to trot or are you doing trot to canter or maybe some of everything? And on suppleness days, working at a walk for 10 min is very different than 10 min of cantering. Then you have what I think of as 'brain workouts' which may not be very taxing physically, but can be stressful mentally.
If you want to focus on fitness, then on a day you think of as 'easy' in terms of physical workload (a "brain day"), you can always add in a period of trot or canter work if its something you want to work on every day. Spend 20 min (or whatever time i takes) doing correct stops, then trot for 2 5-min intervals with walk lateral work in between.
I can talk to you about my training schedule, but I don't even have a ring, so won't be of much help that way. :)