Windows 7 will remain under Microsoft extended support until January 2020.
It's not going to be formally "turned off".
It may eventually become unusable or uninstallable on new hardware.
Newer versions of software that you may use will likely become unusable on Windows 7 over the intermediate and longer term.
If you buy a new computer, it may well have Windows 10 on it whether you like it or not.
If your PC is working well now, you should be OK till at least January 2020--and possibly longer---depending on how long your existing hardware lasts and whether or not you care if Windows 7 is no longer "supported" by Microsoft after that date.
Windows 7 still is the most widely used operating system in the world, so hundreds of millions of PCs are not being upgraded as yet.
You can always choose a non-Microsoft operating system.
Many on this forum are not upgrading and have no immediate intention of doing so. Nothing wrong with standing pat for several years.