I have an MX Master 3. The rubbery material they use on the exterior surface wears really quickly. There's no way I'd consider it BIFL.

I've have the origional MX Master, a couple 2S's, and a 3S (going to order another likely today)...
Function wise, there really isn't any difference between all three versions that I've found, and all of mine still work/charge fine. My reason for upgrading was that my origional MX master started to miss some clicks after years of use/abuse, my 2S's are on my desk and in my bag in use at work daily, and I recently (4 months?) got a 3S from a vendor.
At work I've set users up with probably 20-30 over the years, I've never heard of a battery issue with them and have only replaced one due to a broken charge port.
From the "1" to 2S there was nearly no physical change, a slight color difference, but they nearly doubled the battery life and upgraded the sensor which makes its tracking on any and every surface much better.
From the 2S to 3S the biggest change that took a few days to get used to was how frickin silent it is. My wife nearly killed me a few times clicking away while watching TV with the 2S, the 3S ratcheting scroll and clicks are nearly silent. my biggest gripe would be that they re-arranged the thumb area so back/forward are now in front/behind each other instead of up and down, and they moved the horizontal scroll up a bit to where you almost need to feel for it/intentionally reposition your hand.
That said, I'm kinda in love with the 3S now, and if they could do "something" to fix the issue I have with my pinky getting a divot from how I hold it (every one of my mice has a wear spot about 1.5 inches in from the back right corner from my pinky rubbing) it'd be perfect lol.

2 is similar to 1 but with minor improvements. The design of 3/3S is going well for me, I'm on year 2 and it's aging pretty nicely for me. Some discolouration in the silicone, but pretty much anything in contact with your (sweaty) palms will degrade or discolour over time. Functionally, the 3S seems to be the best. Takes all the functional improvements of the 3's design (USB-C, better ergonomics, buttons, magnetic scroll wheel) and then makes all the switches silent and extremely long life.

I've had a bad experience with the 2S. Mine died within 2 years because the thumb button fell through and kept registering as held constantly which meant moving the cursor didn't work anymore. The weird thing is I didn't even use the thumb button, I guess it disloged itself because of wiping with wet wipes too much.

Function wise the mouse is good though, plenty of buttons and the secondary scroll can be useful sometimes. I used to use it on my phone sometimes too.

I have owned all three. Once I bought a wired swift point with onboard memory they all went in the drawer. I miss the scroll mouse wheel, however none of these mouse compare to this imo.