As some of the people who were here back in the old days will remember, I got a Zip in 2000 that lasted for about 18 months before it got the "silent click of death". Never been a real big fan of Zip drives after that, however really, after all this time I'd imagine that any Zip thats lasted until now is probably pretty safe. I have a Zip in my Beige G3, and while its slow (my previous Zip was a Zip 250, this is a Zip 100), I can't fault it.

Really, for long term archival, your best bet is to have multiple copies of stuff stored on different types of media.