Any file file worth having is a file worth waiting for.
I've waited for a file to complete for almost 2 whole years, one last mp3 to complete a rare cd (the first song). It never did and I lost the temp part file. Sadly you can buy the cd for $3. And it ain't better than decent.
Longest I think I completed a file would have to be 7-8 months. I ve waited longer but most never complete
Unlike torrents where a dead link is usually dead forever, emule tortures you with tempting "seen completes" and "bytes received".
BUT rare filehashes can sometimes stay alive for near decades... and get passed around more than your mother's!