Re: How long before....
Many years ago when I discovered how to use the hosts file, I too blocked many sites with it, including Microsoft's.
Some years later, I noticed the references to MS's sites were hashed/commented out. After a little investigation, I found that MS were editing that file without permission. No matter how many times I tried to block them with the hosts file, every attempt by the Windows computer to access a MS site included a modification to my hosts file.
To fix that, one had to set the file to 'read only.' Not sure if that still works. Anyway, that was back in the days of dial-up. Hardware firewalls work best nowadays :)