I find that I'm enjoying myself when my character is meaningfully involved in a plot that makes progress/has a new development every 1-2 weeks.
Meaningfully involved: I mean that my character is making contributions to the outcome of the plot and not just sitting in on meetings/watching other people make decisions. I also separate out Big Battles where my character is just one of many and her contributions don't count. Court scenes don't count. Attending council meetings where my char is in My characters actions have to count.
A plot: Generally I mean one. One plot at a time. I'm a very linear person, I can't help it. I get stressed when I have to divide my attention between too many things, which is why I can generally only maintain one character on a game at a time. However, I have been able to maintain a personal development plot, along with a group plot, so it's not impossible, I just don't want to have too much shoved on me at once. Neither do I want to be sitting around twiddling my thumbs and feeling like I have nothing to do or no way to contribute. I've left games for both extremes. Heck, I've left a game for feeling both ways at the same time.
I have no preference about the scope of the plot. Big or small doesn't matter so much as the way that my character affects it and the way that it affects my character (See above).
Progress every 1-2 weeks: Pacing is hard. Something needs to happen regularly so that you keep investment and feel like things are moving forward. However, if things progress too quickly, you don't have time to RP about it and make good decisions. For me, personally, I've found one development every 1-2 weeks to be the sweet spot where I regularly have something new to share, but don't start feeling overwhelmed. Of course, this varies. If my char is pulled out of all RP while the plot is going on, I want developments more often. If the next step requires a lot of thought and planning, slowing down or breaking into smaller chunks is preferable (This is why I appreciated Firan's Res-day system, even if I didn't always like the resolutions).
This of course, is just what I prefer. It doesn't quite answer what you were asking, but I hope it's helpful!