Back up runtimes regularly and archive them in secure off site storage.  It's even easier if you keep everything that doesn't have be installed to main Poser runtime in external runtimes on an external drive.  If you internal drive dies, you don't lose any of your runtimes or their content.  Only thing you have to do is re-install Poser and add the external runtimes to the library list.  However, it is a good idea to regularly back up and store a copy of the runtimes off site because even external drives can fail.