I am NOT in any way shape or form any kind of a computer software geek.
I am just a computer user.
There is nothing wrong with staying on XP. I liked XP, and I also had the service paks. When the XP ran slow I would just reformat the drive and reinstall. I created a backup system with all the programs I ran and reinstalled everything all at once. Easy Peasy. I think even networking home computers was a lot easier than todays awful stuff like win 7 and win 10 - horrible - horrible - horrible. Oh but it is well protected. It's SOOOO well protected that the user cannot even get into it. I HATE networking 3-4 simple home computers on the horrible new stuff. I never had any issues with XP networking once set up.
Of course the software does not support that notion, they make money on software upgrades and there is more built in obsolesce in software than anything else in existence. With THAT said - there WILL be a point where new software upgrades, of other stuff will not work on XP. Stuff like CAD, Sketchup, Quicken, Corel, and whatever you use regularly.
Then, there ARE little niceties in the new operating systems. You get used to the new stuff and don't really notice is until you go back sometimes. I did go back to XP to get my OLD CNC machine ready to sell. That's when you notice a lot of stuff.
Internet is not going to be very tolerant of XP any more. Some of the new web sites are going to build to run on new operating systems and may not work on XP.
The really big deal on the internet is the adware, and spyware. THAT stuff is gonna kill ya. It will get into you computer and get into every little nook and cranny in grind your computer to am absolute stand still. That alone will force you into a reformat and reinstall every month or so.
All in all, yes I agree, the old worn out shoes ARE comfortable, and I am a CHEAP CHEAP New England Yankee. I absolutely HATE to support computer software upgrades - BUT - they DO have us over a barrel. Microsoft claims that Win 10 is the LAST upgrade? No such luck. Will will upgrade to Win 399 some day.
Soo - from a NOT a geek perspective - Go with the upgrades - you are going to do so someday anyway. In the long run you will be better off.