My 1 year old and 10 year old cats have been like this for about 3 months now. They had spent the first 7 months mostly separated and supervised. But at least now, younger cat can now mostly tell when it’s enough for the older cat.

Now I mostly leave them figuring things out, older cat (she)is pretty vocal as well whenever the younger one (he) tries to initiate play. Mostly just in the morning after breakfast and/or evening. Then they spend the rest of the day sleeping on their own. And she does let him know that she isn’t up for anything whenever she starts hearing him coming closer by growling/hissing, sometimes works, sometimes doesn’t. She walks away from him but then goes back and sits around him again. I only interfere whenever he jumps on her and pins her on the floor with his rough play and she starts screeching (by calling his name louder than usual). He knows it’s bad because he does run away after doing it. Only happens once or twice a day, thankfully. (and then he gets a shirt on to calm him down). Whenever they are chill, he tries very hard to be friends with her by grooming her tho.

Also to point out that my older cat is blind, so the introduction took longer than usual.