Hi, magicnote, and welcome to FlyerTalk.

(I know, the account's from 2005, but I've always wanted to do that for someone's first post. )

Yes, VX pricing does vary at times, as has been described in the thread. And unfortunately, Virgin America is unlike United, Alaska or Southwest, and similar to some other airlines, and won't always give a credit back if the fare drops (expect within the 24 hour window of purchase, as you were told). There's really not a consistent standard here: some airlines do refund price drops, some offer credits, some do neither.

FWIW, I've used YAPTA and other tools to get credits back on AS/WN- it's already gotten me back some cash. You might look at that or at Farecast (which will project airfares for you) to help with your purchasing decisions.