When the assistant trainer was riding Tristan last summer, I told her that he is a horse who needs processing time. He functions best and happiest when he has a day in between intense rides. He is not a horse who needs or wants work seven days a week.
AT remarked that she'd often heard people say that about their horses and had never found it true, and then a few days later she came back to me and said "Wow, it's true!" Giving Tristan a day completely to himself in between training rides resulted in a totally different horse: more forward, more willing, and he had clearly digested the mental lessons and come out better for it.
Granted, my current once-every-ten-days schedule is not ideal either! But Tris would do very well on a solid, consistent, 4-5 day a week schedule with two, mayyyyybe three, of those days as a hard drill. The others would be non-brain work: trot sets, hacking out, you name it.
It works well for me, since I'm not in a position in life (or quite frankly, a desiring frame of mind) to have a horse that NEEEEEDS that 7 days of work a week.