I've been happily using W8.1 for years and years. Resisted the jump to 10* partly because no need and partly because, at the time it came out, lots of people (on here!) were criticising it. Now I reckon that's just what people do when there's a new OS. So now 8.1 is coming to the end of security updates, next Monday in fact. MS are recommending to jump to 11** and trying to sell me certain machines for this reason, mostly HPs.
But is it necessary? I guess nothing bad is really going to happen if I carry on using 8.1? I'm not too keen on upgrading the OS on this machine, that sounds like it probably has too much potential to go totally wrong and end up with nothing.
*And 9? Was there never a 9? Or was it released, found to be unusable and promptly withdrawn, thus the next version was 10? Or maybe 9 is an unlucky number in Microsoft world?
**Why was this version not called Microsoft SpinalTap?