The only problem I've had with using an external drive for runtimes is that if that drive isn't plugged in when you start Poser, it drops all the runtimes on the drive and you have to reconnect them.

Yes, that is kind of a pain. My Western Digital external almost never drops off, but my Maxtor does, quite often. It's just random. Sometimes when I turn the computer on, the Maxtor external doesn't show up. Sometimes it just drops off randomly. Turning it on and off again fixes the problem, but if I don't realize it's dropped off, and start Poser, I have to reconnect all the runtimes.

I've gotten in the habit of only hooking up the runtimes I need, though, so it's not a huge inconvenience for me. I'm always adding and removing runtimes anyway.

Though it would be nice if you could arrange your runtimes in Poser. Or even if they automatically alphabetized or something.