I find as I get older I tend to play fewer chords rather than more, but maybe to change them a bit more often and play them in different places, to give the old fingers a rest as much as anything.You watch the one singing the song (if it's a song) to get the chords when you don't know them, but just as much to check exactly when the singer is going to change them. Some people like to rush on with a song, some like to linger between lines for example, and that can change from verse to verse. It's the difference between playing a song as a song, and playing dance music. I know some good musicians who never seem to appeciate that difference.
I tend to screw it up a bit sometimes for people watching me, because, when there's more than one guitar, I'm likely to capo up. Not to stop someone following me, but because I like to avoid getting a crowded sound. In fact when I'm watching someone else, to get the chords right, most times I'll be using a capo anyway and playing different chord shapes.