@kcheraziYes that seems basically right. At some point there is a break even to an annual plan. 

A trick to minimise the cost is to suspend it for the next month the day after you reactivate it.  Then unsuspend immediately before your next month's trips or sooner if you have a trip that overlaps the month end. That way you delay any month until you actually need it.  Garmin let's you start a month at any time but it is a prepaid month so you can only suspend starting at the end of that period.