What happens:
* I get a reminder dialog for an appointment that is due. I do not close or dismiss the reminder. I want the reminder.
* I log out.
* I log back in, and restart evolution.
* Hours later I get another reminder for another separate appointment.
* My original reminder is gone, destroyed, lost. I never see it again. 

What should happen:
* My reminders should only ever go away if I dismiss them, or if I snooze them (in which case they should come back after the specified period of time).
* If I log back in, and there are reminders which I have not dismissed, then they should appear again, and they should keep on appearing indefinitely until I explicitly dismiss them. The only way reminders should go away permanently is I take an explicit action to dismiss that reminder.

Comment:
* Reminders about events that affect you is exceedingly useful data to users, and losing such a reminder is (to me) absolutely a type of data loss.
* Outlook gets this right. Reminders persist forever until you snooze or dismiss them. This is the IMHO the correct behaviour.

Other information: