I just purchased two kits....total four units.  Two of then on the third floor kept disconnecting when no data was going through....that is just plugged into the wall....no PC, etc

After several contacts with TP Link Support which did not solve the problem, I was finally able to figure out what to do.

Either connect a powered switch to the adapter or turn off the power saving feature.  

I did the latter and have found that my powerlines do not disconnect when not in use.  I have yet to determine how much power they draw.