No problem layering Perlane with Radiesse, at the same time or in subsequent visits. You definitely do not need to wait for one to wear off before injecting another type of filler. If you are thinking about making a change from one to another, it is often best to do it before one has disappeared completely so you don't have to go through a dramatic before and after...you can do subtle, more frequent, fine tuning treatments.
Hope that helps.
Dr. Grant Stevens