5 years with original w8.1 install !

but at least Win8.1 is an improvement over Win8 (8.0) and Win10
I use it on a Toshiba Satellite C55DT-A (late 2013) touchscreen laptop (heck that laptop came with 8.1, not 8.0), along with using Open Shell (the successor & fork of Classic Shell).

even with the latest monthly rollup updates, Win8.1 still runs stable & well on the Toshiba laptop for almost 8 years

 

People are making alot of claims here but then again I will say this if no one else can reproduce these benchmarks on matching hardware and setups - of which they are artificial and not everyday usage that is just that Benchmarks. That's doesn't tell much of performance when working 24/7 under pressure. Benchmarks can be made to look as one wants them to look.

I've installed Windows 10 pro x64 on Dell 1525 but then again I update the hardware to work with Windows 10 when originally this was a XP O/S laptop. So there are lots of in and outs that are missing if one keeps talking benchmarks.