Hi StanL
I can only speak to the predatory mites in my soil (Hypoaspis miles). I added them to my soil three grow's ago and I re amend my soil each run, this last time my soil was very hot to the touch after amending it. It seem to take a couple weeks for the mites to bounce back but I think they like all the amendments as the population always comes back stranger than ever a few weeks after. So I suspect most of your beneficials will be fine, unless you are talking about cooking in an oven, then it should kill almost everything.
I think I read somewhere a while back that nematodes need to have a host to survive / reproduce. So once they are done their job they die off and need to be re applied.