Not sure how often it phones home, but nine days is the most you have between call-ins, according to EnglishBob, who tested it.If Poser can't make contact in that time, it stops working. Even subscription software like Photoshop gives you more time than that.

Not buying the trial period as an excuse. There's a ton of software that has trial periods but doesn't need to phone home. Seems like it would be simple enough to turn off the call-in feature once you've purchased the software.