A new Debian Stable comes out when it is ready - after a long freeze. Originally (from memory) Debian stable was only supported until the next stable release w

A new Debian Stable comes out when it is ready - after a long freeze. Originally (from memory) Debian stable was only supported until the next stable release which could be anywhere from 18-36 months later (release timeframes seem more consistent these days). Then they started supporting an oldstable (the previous stable release) for an extra 1yr timeframe. Debian LTS is a newer initiative, but it doesn't quite have the same security service level as say Debian Stable. Not all patches make it to LTS, and those that do arrive noticeably later. Debian is trying to find ways to improve this though.