The other branch is the Legacy GPU version and covers the 304.xx, 71.86.xx, 96.43.xx, and 173.14.xx series, which is quite a lot right now. NVIDIA has decided to shed some light on these versions and explain to the users what will be kept and what will be deprecated.
“The Linux 340.* legacy driver series is the last to support the G8x, G9x, and GT2xx GPUs, and motherboard chipsets based on them. Support for new Linux kernels and X servers, as well as fixes for critical bugs, will be included in 340.* legacy releases through the end of 2019.”
“The Linux 304.* legacy driver series is the last to support the NV4x and G7x GPUs and motherboard chipsets based on them. Support for new Linux kernels and X servers, as well as fixes for critical bugs, will be included in 304.* legacy releases through the end of 2017,” reads the official announcement.
The other versions left are 173.14.* and 96.43.*. These two branches have received support for the newly released X.Org xserver version 1.15, but no other releases are planned. The 71.86.* branch will no longer get any support.
This means that right now, all the NV4x and G7x GPUs will be supported by NVIDIA until 2017, and everything above them will be supported until 2019, which, needless to say, is quite a long while.
It’s also very likely that other new branches will be launched in the next few years, so the Long Lived Branch and the Short Lived Branch will most likely be replaced by much newer releases.