I'll ask the counter question - how often did you reinstall Windows? Windows - a fairly stable system, if with it (as with any other OS) properly handled. I still have Windows XP installed on one of my computers (since 2010) without antivirus, firewall and other add-ons. Yes, not on one - on the second multi-boot with Windows XP, Windows 7 and Xubuntu. There is no antivirus on any windows. And this despite the fact that all work and interests on the Internet (including pornsites sometimes;)). So what? 5-6 years at least. Linux I use from 2011-2012 - on all 3 computers installed Xubuntu as the main system.
The last installation after buying another laptop:
$ sudo tune2fs -l /dev/sda1 | grep create
Filesystem created: Wed Oct 19 21:29:42 2015
Everything depends not on the system, but on the person. Accuracy, care and the creation of backups - this is the guarantee of longevity of the operating system. Linux can be spoiled by one careless command
$ sudo rm -Rf --no-preserve-root /
Always think what you are doing, ask, if you do not understand, look for information on the right questions - and your life will be long and happy