I failed to upgrade a friend’s Fedora 15 last year so I left it running there untouched, however, Fedora announced EOL of 15, which means I have to risk leaving it up and running without any further patches, or I have to do an on site upgrade.
Personally I prefer an on site upgrade to make sure everything is up-to-date, but my friend may not like this as the rental (i.e. hosting) will be ended in less a year.
Anyway, waiting for reply now.