My Win 7 box will run until no more security updates come in 2020.
By then you should be pretty good at reinstalling your system from a clean image and having your data backed up, for that odd time when your box DOES get pwned. Which you really have to try hard to do nowadays - gone are the days of some random worm taking over your box just because you hooked it up to the internet.
And besides, hopefully Flash will be totally dead by 2020 and a major security threat will be gone.
Intel CPUs are not defective, they just act that way. -- Henry Spencer