YES I hate this too.. it makes websites like mine look bad, or at least people more weary to join solo girl websites because they've been burned in the past. Another version of a website that doesn't update is websites that recycle their content.. they take down the old stuff, only letting you view so many pages of porn at a time, then eventually it gets posted as new stuff:/
There are ways you can look out for such a thing: Are there signs the actual girl is active on her website? Is there a blog that gets updated regularly, is she doing webcam shows on her website weekly, is there a calendar somewhere where you can see the next couple weeks/months of updates scheduled? And you can always ask a girl on Twitter too
(btw I update 6x a month.. just sayin