I only have 4GB of memory, and I always set up swap, but frequently if I have several tabs, or a really large Google Doc open, it seems as if my system has crashed. However, I think it is really just thrashing, and sometimes if I come back in a couple of hours, I can get control back and close some tabs.
The problem is that while the system is thrashing, I cannot get enough resources to (say) open a konsole and run top, to give decent diagnostics or even systemctl reboot to just give up. I either have to wait (sometimes up to several hours), or hit the power. The laptop I use most frequently has a broken SysReq button, so I have not enough data points to say how REISUB will work while thrashing.