Interval International (II) offers an incentive bonus to owners of high-demand weeks who deposit them with II. That bonus is an Accommodation Certificate ("AC"), which can be exchanged for a week through II. Your exchange choices will be limited and generally won’t be prime season weeks. Thus, there are effectively blackout dates and blackout resorts. The restrictions for your AC will differ from the restrictions on some other ACs.
In addition, you can use your deposited week to exchange for another week.
During the last 59 days (“Flexchange”) before a week for which you would like to redeem your AC, you can see almost any week available in the II exchange system, other than those weeks restricted for various resort system (such as Marriott) internal trading preferences.
The cost to redeem an AC ranges from $199 to $299: $199 for a studio, $249 for a 1BR and $299 for a 2BR.
The AC is valid for one year from the date it is issued, which is usually soon after you make your deposit. Thus, to use your AC, you must reserve and take your additional vacation during that one-year period. That suggests some strategy, since the longer you wait before depositing, the longer you will have to use that AC once it is issued. The challenge is to balance that additional time against possible reduced trading power for your week due to delaying your deposit.
There is no guarantee that you'll receive an AC every year you deposit your week. The demand for your week could change, possibly leading II to stop offering an AC for your week. Also, you won't get an AC if you use the request-first method for requesting an exchange, under which you hold onto your week until you get an exchange that's acceptable to you.