Hi there,
We have been using in our office the 2016 max version for more than 3 years now (90% for archviz).
Is there any reason to switch to newer version?
I have not followed the updates for the 2018 or 2019 versions … are there still a lot of annoying bugs is those newer versions that Autodesk have not fixed yet? 
It’s getting more and more stable and are also faster in therms of viewport performance.
There are some new features but I’m not sure if they’re useful for you. Just read the what’s new sections in the help files.
They have a fluid sim now, also there is the data channel mod, the bbm map and osl to name a few.
They fixed alot of bugs.
I’m on 2019 now and I only crash 1-2 times a week. It was about 4-5 times a day with older versions.
I’ll try 2020 for my next project since in 19 I have some annoying performance problems when I switch between polygon selection modes.. And the new champfer mod in 2020 looks pretty awesome.
All in all they seem to rather fix bugs and performance issues than creating tons of new features these days.
I went to MAX 2017 for 4K support, but it was a mess and I crashed 3-4 times a day. They made some good efforts in MAX 2018 and I crashed a couple of times a day. Now MAX 2019 is as stable as MAX 2016. However, if you don’t need 4K support, there isn’t much reason to switch. I am on subscription, so I’ll eventually move to MAX 2020, but again, really no solid reason other than I can.
Yeah I have that in any 3dsmax version after a while. Format and reinstall seem to work wonders.