Checking for Changes in the Mobile Manifest

I've come to realise that the way I'm checking for changes in the [url=http://www.bungie.net/platform/Destiny/Manifest/]Manifest file[/url] is unreliable. Is there a reason why simply checking against the manifest version (every 5 minutes or so) isn't going to correctly tell me when I need to cache the manifest again? How are other people checking for changes, or is everyone just doing a scheduled pull down of the database files?