CAUTION: Nobody has addressed it yet and you might be getting misled.
You can combine points ONLY if the two contracts have the same base contract number. That happens when you do a true add-on through Disney. The two different resorts will have the same use year, and will have the same base contract number, but with different extensions.
Example: you purchase 150 SSR points from Disney, contract # 12345. This becomes contract 12345.000
Later you purchase a true add-on 50 point contract from Disney for a different resort. This becomes contract 12345.001
At 7-months you have only ONE contract and can use the 200 points any way you want.
However, if you purchase resale, the contract most likely will get a completely different contract number. If they are different use years, they definitely will have different numbers. If they're the same use year month, you can request Disney add it to your original contract as an add-on, but you must request this from them. They will not do it automatically.
The points are NOT combined but remain separate contracts. In this case you would have a 150 point contract and a totally separate 50 point contract.
Now, suppose you wanted to use those points for a reservation that takes 35 points/night for 5-nights. That's 175 points. You have 200, but your 200 is actually 150 + 50.
You can use the first contract to get 4 nights for 140 points, and use the 2nd contract to get 1 night for 35 points, and then you have to link the two reservations together, otherwise you'd have to move.
This leaves you a balance of 10 points on your first contract and 15 points on your 2nd contract.
This is a very important distinction between buying resale and buying an add-on through Disney.