At What Stage of Decorating Should I Use My Dehydrator?

I don't find that my cookies dry out at all in the dehydrator, so I don't worry too much about how much time they spend in it. On average, I would say my cookies are in there for 3-4 hours. I set the dehydrator to 95 degrees, at temperatures above that I often have issues with butter bleed because the cookies get too hot. 

I use the dehydrator at every step. It allows you to much more quickly move onto the next step, the icing will dry shiny, and problems like craters and bleeding are much reduced. Using it for the whole process helps you to best take advantage of what the dehydrator can do. 

Thank you so much for clarifying. I am definitely going to invest in a dehydrator after all I've read. I have craters constantly, and if this helps I will be thrilled. Also, just to speed up the process. I am sooo slow at decorating so anything will help!

I agree with what Happy Loris said for the most part, but since I don't have to package cookies for commercial sale (where they need to be completely dry before putting into bags), I primarily put cookies in the dehydrator to fast-set the base coats (and give them some poof and sheen) or when I've flooded small angular areas that are most prone to cratering. I typically won't put them back in just to dry small details on top, for instance. That said, my cookies' max time in the dehydrator is probably not more than 20 minutes. In this time, I see no material change in cookie texture.