a caching question...

[eluser]Crag[/eluser]
New to using Codeigniter (been a lurker for ages) so pardon the noob question.

If I cache a page using $this->output->cache(30); and the page content changes, will it update the cache or does it wait until it expires?

I have few pages the rarely change.. but it is possible that they will.

Thanks in advance-

-crag