As be positive says, it is an individual thing.
My own circumstances dictate what I can and can't do as work full time with a long commute, my hacking isn't great (all roads unless I box somewhere) and traffic is too busy during the week to ride out.
During the summer I school 3 times during the week and then lunge and in-hand one day, if I can get out to a cross country hire, SJ training show or jumping lesson I do that in place of one of the flatwork days. weekends are for hacking, shows or lessons
Over winter then I ride before work, usually only manage to get half an hour ridden work in, same goes really that I try for 3 x a week and might include a pole session plus then a lunge / in-hand. weekends for hacking / shows but I might get out the odd week for an arena hire or lesson during the week if my work schedule allows.
M maintains a certain level of fitness doing this, if I am planning to do a particular activity (hunter trials or similar) then I will increase fitness for that.
In terms of my own strength and fitness - I am in the gym 3 times a week working with a PT who understands horses and riding who writes me 6 weekly programmes and we re-evaluate if I feel I need to change something then we work on that