I think that Jazz is just another feed client, if you re-install you will loose your cached data about the feeds you've downloaded. Unless explicitly stated, there is no need to upgrade your Eclipse workspace between Jazz milestone builds.
Jean-Michel Lemieux
Jazz Source Control Team

The feed entries that you see in RTC are generated dynamically from
state changes stored (temporarily) in the database, rendered into
RSS/Atom on demand (and stored in non-persistent, LRU caches on the
server). Depending upon the item type that the notification targets,
that change event could persist in the database for 2-30 days, available
in feeds for that amount of time.

To determine whether or not there's a problem with the local cache that
your RTC client is using: copy the URI from the feed in question (either
from the Team Artifacts view, or Team Central), and paste that into a
browser. If you can see events in the browser, but not in RTC, then it
means that there's something going on in your client. Confirm that the
filters on those events you're view in Team Central are as you expect.

-- Todd (Jazz Team)

dvdmunni wrote:

But with the local (cached) data removed, shouldn't the feed at least
show the most recent items.

(in my understanding a rss feed is just an xml file with a couple of
entries)

How long do older items remain in the rss feed ?

regards

Daan.