Canonical has decided on reduces the official support for non-LTS Ubuntu releases to NINE(9) months starting with the upcoming Ubuntu 13.04 release
As for my personal opinion, this changes is long overdue since 18 month support time for a SIX(6)-month cycle release can be considered as long, thus it is better to invest those precious time and effort into producing newer Ubuntu release.
These changes has been voted with presence of Ubuntu Technical Board and will be effective starting with Ubuntu 13.04 Raring Ringtail onwards.