Primarily an eventer, but also dressage and H/J.
I always start and end with 10 minutes at a walk, so that is 20 minutes right there,
If I am doing conditions (interval training) that might take 20-30 minutes, so a total of 49-50 minutes.
But for working in the ring (flat or fences), or riding on trails (but not interval training), it is usually 30 - 50 minutes in addition to the walk warm up and cool down, so a total of 50 - 70 minutes.
Unless I am starting a green horse, or rehabbing for an injury, I don’t think I am ever on a horse less than 30 min.
I try to ride a minimum of 3 days a week, but typically 5 or 6 days a week.