Marriott and CSA have changed the way insurance is sold for your timeshare stays. In the past, the insurance was valid for all vacations within a 13 month time period. Now the insurance is purchased per trip. Your insurance cost is based upon the number of timeshare weeks that you want to insure. For example, to insure 2 weeks of a timeshare vacation, you will pay $199. Should you need to cancel for a covered reason (such as medical) then you will be reimbursed up to $3,000 in maintenance and exchange fees.
I do recommend that all owners insure their vacations as the unexpected can happen. Call Marriott Owner Services or choose Protect My Vacation from the owners clubhouse website to purchase.