Being the nice dummy I can sometimes be, I had misunderstood the way MagpieRSS' cache feature was coded. The default value for the cache in my taga.licio.us script was set to 60… seconds, not minutes. If you are a user of my script, please update it and change the value of MAGPIE_CACHE_AGE to 3600.
(taga.licio.us is another PHP hack for del.icio.us, allowing to retrieve links for a given set of tags)