Here's a page showing the End Of Life dates of Fedora Versions:
Once a version has reached End Of Life, you can expect that all support for it in FedoraProject has stopped. Some repositories may carry updates for a time after that, depending on their preferences, but eventually yum won't work and you'll have to either consider updating to a current version or trying to maintain your OS with outside support.
Since dependency problems can crop up, I'd suggest checking here: http://rpm.pbone.net/
for packages and potential dependency problems.
Another resource will be the Archived Forum, closed to posts but available for searches, and the Search engines within the Forum. I'd suggest using the Advanced feature and older search dates to get best results.