I have 16GB of RAM and use Debian 13 with XFCE4, memory usage goes up to 4-8GB over multiple days.
When I do power off I usually save the session before shutting down.
I have lightdm version 1.32.0. Will take me another week to make a screenshot of the usage, but be patient with me and I'll produce one if necessary (I've switched over to GDM for now, but will switch back if one is wanted).
Unlike the other issue on here #84, it was not Xorg using up all the memory, it was lightdm under the task manager.
Let me know if you need any other information.