If I got your correctly
1. If problem is fixed expected is that alert WILL clear in vrops (if not - for example if you alert threshold is 85% and NOC cleaned disk to be 90% - this means either NOC has not fix the alert or threshold is incorrect), so if you disk will fill up -- next alert will be raised
2. Yes, it's true to some extend. I would believe it should be your ticketing system to send a reminder on the open alerts.. Or you can use notification on updated alert (each time when cancel cycle is out you should get a notification send, you may want to test and possibly after 10 notification raise the alert severity..