The problem is, Keef, that the 'baddies' will eventually find a way to sucker your SS's into catching a cold - and they are very unlikely to know it has happened. Isolation from the internet is the only safe option long term.
I suspect the 'shock/horror' your oldies will feel having to shell out for 7 or 8 (or 9) may well dent M$'s attractiveness to the general public - and industry judging by the reported proliferation of XP there.