When I click on update, only my main language (english) sites are deleted. Spanish and English translations as set by Qtranslate, are left until they expire.
So instead of deleted the cache only for http://openmtbmap.org/downloads
I would also need to have the cache deleted for http://openmtbmap.org/de/downloads
and http://openmtbmap.org/es/downloads
...
Would be great if Quick Cache could support this. Other caching plugins like Supercache do support this. (though Supercache is slower for me). Quickest for me is hypercache, but it does not integrate very well with s2member - so I stayed with quick cache (also because I do like, that one can configure it to purge the single page/post & frontpage (but instead of 2 version purged, I would need all language versions purged too).
Related to this I am not sure if this has the same reason, but with expiry set to 4hours, my cache folder has 2000 files in it (but there are only bout 200x3 pages to cache) some dating back 7 days (the last time I manually cleared the cache folder). I do believe expired sites that are translated may be left over.
However difficult to analyse, as the naming of the files is random, and not structured like other plugins do.