On May 31st, FreeBSD 5.5, FreeBSD 6.1, and FreeBSD 6.2 will have reached their End of Life and will no longer be supported by the FreeBSD Security Team. Since FreeBSD 5.5 is the last remaining supported release from the FreeBSD 5.x stable branch, support for the FreeBSD 5.x stable branch will also cease at the same point. Users of any of these FreeBSD releases are strongly encouraged to upgrade to either FreeBSD 6.3 or FreeBSD 7.0 before that date.
Please note that the End of Life dates for FreeBSD 5.5 and FreeBSD 6.1 were announced in May 2006; and the End of Life for FreeBSD 6.2, which was originally announced as January 31, 2008, has been extended by four months in order to allow time for users to upgrade.
The FreeBSD Ports Management Team wishes to inform users that May 31st (the security team’s End-Of-Support date for FreeBSD 5.x) will also be the end of support for the Ports Collection on both 5.5-RELEASE and the 5-STABLE branch. Neither the infrastructure nor individual ports are guaranteed to work on these FreeBSD versions after that date. A CVS tag will be created for users who cannot upgrade for some reason; as of that commit, these users are advised to stop tracking the latest ports CVS repository and instead stay with the version as of that tag.
Source & more info (01-04-2008)