My suggestion is to read the thread on washing yeast. It is a sticky in the fermenation and yeast heading. That will give you all the information you need. I have washed many yeasts over the years. They seem to keep for a pretty long time. Freezing them is not a good idea, unless you do it the proper way.
Primaries - all empty
Secondary - Several Hard Ciders
Bulk Aging - Brewtopia Barleywine