In addition to /var, tmpfs should also be used for /tmp and similar. That should lengthen the SD card's lifetime immensely.
In fact, I didn't notice the change until now.
Copying through /tmp is a frequently used method for transferring files between users on a multi-user computer.
It is said that the Linux kernel will include soon an improved version of tmpfs, which will allow user extended attributes, within certain limitations.
When this will happen, one of the most annoying misfeatures of tmpfs that has persisted for much too many years will finally be gone away.
Be careful to check inside your docker containers also. It can end up different.
Here is a good article btw, with someone advocating for moving to tmpfs https://ubuntu.com/blog/data-driven-analysis-tmp-on-tmpfs
Logs to log server, if system needs non-volatile writable storage — NFS or second storage device, depending on requirements.
Of course, it is too much hassle for single such system (but I started to use it from very beginning out of curiosity) but uf you have many single-task small devices it is very convenient.