I'm guessing this doesn't capture manual restarts? I have the same experience as the commenter below: Plasma requires a restart a few times per day for me, as the panels disappear and one monitor's (of two) desktop goes black - usually after wake from sleep. This occurs on both machines that I run it on (only common component is Radeon graphics).
That said, it's a single command and not a big deal, and it's a great DE, so thanks for your work.
I will say it's atypical though. We measure session uptimes in months. There is probably a very specific cause that can be addressed or mitigated.