I am not certain if this should be a Java Edition, or Launcher issue, or both – Or even if it is a single issue or multiple issues. If I leave MineCraft running for a significant time (hours or days), it will eventually expire the session login (key?), which makes it give the following error in the logs:

[<timestamp>] Netty Server IO #3/ERROR: Invalid signature for profile public key.
Try restarting your game.
com.mojang.authlib.minecraft.InsecurePublicKeyException$InvalidException: Expired profile public key

...

If I close MineCraft (and the logging window), and go back to the launcher to restart, the launcher window is completely blank. Sometimes I can close it and restart it completely – But on occasion, I have to force termination with "kill" (I use Linux, so the exact semantics of process termination vary from Windows[tm]).

Note that I can continue playing even with an expired session; I just have to ignore the error messages in the log file. But this is sub-optimal, as it causes cluttered log files and may cause me to miss a more significant error/warning.

Ideally, session expiration should be handled much more gracefully. Ask the player to log out/allow the game to log out, and log back in, for example. Just about anything except forcing the player to completely close out all MineCraft windows to restart it completely fresh. Note that, in addition, forcing a restart may also "hide" other potentiall significant bugs such as resource/memory "leaks", which should be identified and fixed.

Also, consider a setting to allow the player to change the session expiration (within reason, such as "From 1 hour to 7 days") time period.