Like others here, I can usually play in multiple games without breaking a sweat, but I try never to run more than one at a time. Based on the responses here, I'm in pretty good company.
I will add that I've started playing in person again for the first time in...*gulp*...decades, so that's taking up time that I normally would have used for more PbP games to join, so my total number of games being played in online is lower than usual for me. I have to say, though, that I love the mixture of both mediums now. PbP will always be my first love for TTRPGs and it allows for more pure, immersive roleplaying than any other style I think, but getting together with friends, rolling dice, killing bandits and eating hot pretzels together over some drinks is a great way to spend an evening too. :)