Someone suggested that you can speed up P5's launch time by creating a "null runtime." Basically, a runtime with nothing in it. You make sure to set that the active runtime before you close Poser, and when you start Poser the next time, it will be pretty fast, since it will only scan the runtime that was active when you closed it.

Not sure if it works; I set up a null runtime, but always forget to set it active before I shut down.