Hell, I'm all ok with this method... but does (different) webhotells take into account the amount used with cache/temp files.
If so, some check should be used, and if not. Cache it all!, and remove the timelimit, some check for the change of image of course, but that all depends if you acctually change images from time to time..
If it's under your user account then there's no way for them to know which parts of your website are cache/temp folders and which aren't. So yes, caches & temp files/folders will be included in your disk quota.
--
Postgresql & php tutorials
http://www.designmagick.com/