I love having 2 horses----but clearly, I do spend more time at the barn than when I only had one.
To keep up with riding 2, I basically ride every day (unless I have to travel for work). On work days, I usually only ride one (alternate days that I ride each horse) —then I ride 2 each day on the weekend. I have some flexibility with my work schedule on Friday afternoons too—so I can usually fit 2 rides in on Friday as well. Or lunge one and ride the other. And I am little bit obsessed with keeping my horses in regular work (my goal is that they get worked about 5 days a week)—but there are lots of fellow boarders that only ride a few days a week and their horses do just fine with that workload. A school master might do great with 3 days a week in work—although if they are older and a little arthritic, keeping them moving (even a short ride) will be better than giving them more time off. I do find that I keep my rides a little shorter, and more focused, if I know I need to hop on my other horse too.
You didn’t mention whether you keep your horses at home, or board them. I should add that I board–so most of the barn work is done by the barn. Obviously, it’s much harder to fit this all in if you have to do the barn work, and maintain the arenas, etc. So that makes a huge difference.
One of my horses is older and more experienced, and I have a youngster. It is so helpful to be able to ride my more trained and confirmed horse while bringing along a green horse. My riding benefits from it a lot, as well as my riding fitness. However, I still workout on top of riding two. So I juggle that with a full-time, demanding job, and hubby. I should add that he does ride too, although he only rides a few days a week—but some of the time, we are both at the barn. And, because he rides, he tolerates my ridiculously time-consuming hobby/sport because he has an appreciation for how much time it can take.
So as far as social events----there is none of that during the week (because I’m at the barn every day after work). I still have time on the weekend if we want to get together with friends. Although, admittedly most of my “social” group outside of work—ARE horse friends. So, if you have a busy social calendar, and that’s a big deal breaker for you to having 2 horses–then it might be better to just take lessons on a school master when you can fit it in.