I think baking them until the tops are just slightly golden and they look set is a good indicator. Cooling them in the oven with the door cracked helps too.
Hey there! I totally get your concern about overbaking mini cheesecakes. Here's a tip that works for me: when the edges look set and the center still has a slight jiggle, they're perfect. Also, remember they keep cooking a bit after you take them out of the oven. Hope this helps!