“Why keep supporting a five-year-old operating system? Because, if you work with servers, five years can be just the start.” OR you might just like your current desktop and want to keep it safe . .
“so Canonical found they had enough 12.04 legacy users to justify offering important security fixes for the kernel and the most essential user space packages”.
Steven J. Vaughn-Nichols
So, version 12.04 (2012-April) is Ubuntu’s oldest supported OS. Now, and for current/future releases (16.04), Canonical will support the OS for up to 10 years . . . . and seeing how OTC’ers (nee Slugo-ites) hate to update (ergo Win XP) . . . this is good news!