it also has to do with the complexity and the size of your model. If your model has mostly straight walls you could for for a higher layer height, say 0.15-0.2.
If your model is very detailed, or organic with lots of curved walls, like a scan, smaller layer heights are better, like 0.06.
I believe that going lower than 0.06 doesn't show much difference, but I could be wrong… it ads a lot of time indeed.