Reply To: It says here that Ubuntu updates every six months
Just like a lot of widely available software, Canonical (just like Microsoft) has a support lifetime policy. Generally, it is from nine to eighteen months for non-LTS releases, and from three to five years for long-term support (LTS) releases. It depends on the specific release (e.g., 11.04 was supported for 18, but 13.10 was only 9), and version (desktop usually 3, server usually 5).
Furthermore, the only supported in-place upgrades are from LTS to LTS (for example, most recently, from 14.04 to 16.04) or from release to release (e.g., from 15.04 to 15.10). This implies if you wanted to go from 14.10 to 16.04, you would have to apply successive upgrades 14.10 -> 15.04 -> 15.10 -> 16.04.