I'm not entirely sure if I get you. Are you saying I should fetch the XP and check if it has changed? It would defeat the purpose of caching a bit. I have an extremely light server running this app and wanted to avoid the call to the site itself. Perlmonks.org is very slow, and making calls to check it everytime would be expensive.
As alternatives I was thinking of (1) A sliding cache window, if your XP updates frequently then I will cache less frequently. But this is hard because it means I have to write a varnish plugin. (2) A feature to allow users to refresh the cache for just their flair. This is slightly more do-able
If you submit it as an issue I will take this up when I can: