support (as in critical bug fixes and kernel&X support) will last until 2017.
please refer to this page to know exactly the cards affectedOnce 304.* becomes a legacy branch (i.e. when official support moves to a future branch), 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.
http://nvidia.custhelp.com/app/answers/detail/a_id/3142
and here the full list of legacy drivers and the supported cards
http://www.nvidia.com/object/IO_32667.html