If you currently have a Mar OKW contract and purchase a resale Aug OKW contract, it technically is not an Add-On, but actually a separate purchase.
People routinely use the word add on to mean they purchased additional points. Technically an add-on is when you purchase more points from Disney and they are the same use year as your original contract. They don't have to be the same resort.
Add-on contracts have a suffix for the contract number. Example your original contract is #123456. A true add-on becomes contract #123456-001 and so on.
When you purchase resale you are purchasing someone else's contract with a different contract number than yours. It's not actaully an add-on.
In a true add-on, points are combined for purposes of banking in regards to banking windows. However, if they are separate resorts, the 11/7 month rules still apply so often it's still necessary to bank specific points by resort if you want to use the 11-month window to make a reservation at a specific resort.
With a separate purchased contract, points are not combined for banking deadlines. Each contract is separate in regards to all banking and borrowing and making reservations at 11/7months.
Example: You have 4 contracts as follows: (1) An OKW 150pts June. (2) An OKW 50pts June true add on from Disney. (3) A BWV 50pts June true add on from Disney. (4) An OKW 50 point Aug contract purchased resale.
Your contract numbers might be something like this:
1. 123456-000
2. 123456-001
3. 123456-002
4. 764987-000
You have two master contracts (items #1 and #4). You have two add-on contracts (item #2 and #3)
Banking: Items 1,2,3 are all combined in regards to banking deadlines. That is the total number of points (250 in this example) determines what you can bank at the different deadlines. Seven months after your use month, you're in the 50% banking window. You can bank 50% of 250, or 125 points, regardless of which contract they're part of. In other words it's 50% of 250 and NOT 50% of 150, 50% of 50, and 50% of 50. In other words say you had used all your points except the 50 BWV points. You could still bank all 50 points since that's less than the 125 point 50% level.
Borrowing: You only borrow when you are actually making a reservation and you can only borrow the number of points needed to complete the reservation. Example you want to make an OKW reservation at 11 months, and need 300 points. You only have 200 OKW points (150+50) so you would need to borrow an additional 100 points. You could borrow 100 from the 150 pt contract, or all 50 from the 50pt add on + 50 more from the 150 pt contract, or any combination you want. It really doesn't matter since these two contracts are combined for all banking, borrowing, and reservation purposes. NOTE: You could not borrow points from the 50pt BWV add-on since those points cannot be used to make a reservation at OKW at 11-months out.
At 7-months you could borrow points from any of items 1,2,3 to make a reservation at any resort.
Finally item #4 is a totally separate contract and is not combined with anything in any way. It has it's own use year, banking window, reservation window. Even when making a reservation you cannot combine the points with your other contracts. These points must be used totally separately. You can use them to make reservations for separate days and then link the days. Example: You want 5 days at OKW for a vacation that takes 20pts/day for 100 points total. You cannot take all your 50 contract #4 points and 50 points from your combined (1,2,3) contract to get the 100 points as that would mean you're trying to use the Aug 50 pt contract for 2-1/2 days and the other for the remaining 2-1/2 days. You could use 40pts from your Aug 50pt contract to reserve 2-days, then take 60 pts from your combined (1,2,3) contract to reserve the remaining 3-days. This would leave 10pts on your Aug contract, and 190pts on your combined (1,2,3) contract. Note if making this reservation at 11-months out, you could not use any of the BWV points.
One way to handle different use years is to bank and borrow the smaller contract and only use it once every 3-years. Then use the larger contract the other two years.
Using your months for example, March and August, 210 points and 50 points respectively.
Year 1, bank the 50 point contract pts into year 2 and make a reservation from your 210 point contract only, using all 210 points.
Year 2, You now have 100 pts in your 2nd contract, and 210 new points from your 1st contract. Borrow 50 pts from Contract #2 to give you a total of 150 Contract #2 points. Make a reservation using those points. Bank your 210 point contract #1 points into the next year.
Year 3. You have no additional points from contract #2 as you borrowed them the previous year. You have 420 contract #1 points, 210 from the year's allocation, and the 210 that were banked from year 2. Make a reservation using these points.
And so on.
It's not really as complicated as it may seem, but does require some management on your part.
If you purchased a 50pt Aug contract, and then another 30pt Aug contract, Disney may or may not combine those into a master contract and add-on. I haven't heard definitely what they're doing. If they didn't combine them, they you'd have 3-contracts that all had to be managed separately.
In any regards, the points from a March UY and an August UY are never combined in any way in regards to banking, borrowing and reservations.
Hope this helps.
