Rated 4 out of 5 stars

Add-on works as advertised, but there's a bug: when setting a reminder from the drop down list, it is saved. But when setting a Custom reminder, it is reverted to the default (0 minutes) on saving.

This review is for a previous version of the add-on (3.1). 

I'd suggest contacting support on this issue. If the reminder is more than 28 days before the event this may be a server side limitation