Why do my calendar notification disappear after a few minutes?

I just upgraded from a Galaxy S3 (I know behind on the times) to a Galaxy S7 Edge. I love the phone but...on my S3 I could set something in my calendar and it would go off and I could leave it in my notification bar for days (I use these as reminders)...with my S7 Edge I set a calendar item and I get a notification but after a few minutes the notification is gone. Is this a setting somewhere? I have tried playing with the notification settings and can't seem to figure this out.

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