I've still got an old WIN 95 laptop which works fine as long as I don't take it out on the internet (too susceptible to viruses there), and I think that machine is about 7 years old. I've also got another not quite as elderly desktop purchased in January 2000 running WIN 98 SE and it is still useable, although there are things it can no longer handle. A friend's father recently finally decided to stop using his still-functioning old WIN 98 1st edition machine and jumped into a PC with XP Home..... He's been a long-time AOL user and now is about to ditch that and get a broadband connection. Unfortunately I was not around at the time he made the decision to buy a new PC or I would have steered him into a Mac! He would have been very happy with an iMac.... Too late now. Actually, though, he said that he's having some problems with his new HP, that something isn't working, so maybe if he does wind up returning it he can go with an iMac after all..... 🙂
In all of these cases, yes, his and mine, the elderly machines were always turned off when not in use. I still do that with my Macs; if I'm around the house during the day and just not using the computer, I'll leave it on, but if I am going out for a while I always shut it down, and at night I shut it down, too. I am just more comfortable with that than with the "sleep" function, and I think it is better in terms of RAM, too, as then the RAM is fresh when you start up the machine again.
OTB