Thank you for your response, Peter!

I think reinstalling the OS every 2 years is necessary only on Windows, Linux - not so much. As other reader mentioned, you can just delete cache files in Linux and it will be as good as new. But in case of Windows, I have had some horrible experience with some machines that were so bloated after years of use, it took like 10 minutes to just show the folders on C:/ drive.

But thank you for mentioning your "continuous updating" method, I will surely try it out!

And I agree with you regarding Office, it's really a pity that there is no good alternative for those programs. Hopefully this will change in the future. LibreOffice is a good option, I think it will completely replace MS Office in following years.