For every operating system there comes a time in its life where Microsoft deems it too old for continued support. This is called "End Of Life" (EOL) for an operating system. Operating systems often last a very long time, compared to the average computer and so you may find that even after a new OS has been released you still prefer your older one. This is perfectly fine but after two or three operating systems have been released since the release of your currently used one, then it may be nearing its EOL.