It is a bit confusing. Let me see if I can explain it, as it was explained to me (almost made sense then).
Firstly, no you do NOT have to make a decision on using the developer points in the next 2 weeks.
Developer points, based on when you bought need to be used within the next year (prior to Sep in your case). The only catch is you can only make reservations using developer points in the 7 month window (not 11 months as you can at your home resort).
I bought on Sep 13 and got single developer points. Here is what I did:
Booked a 2 bedroom suite and 2ea studio suites
(couldn't get a GV, I think they are hard to get at 7 month) for mid march 2008 using the following points:
2006 points
2007 points
developer points.
This reservation was made within the 7 month restriction and I used them at my home resort SSR (mainly because of availability). I will still have my 2008 points in reserve. Pretty good deal if you ask me.
Please make certain that you tell Member Services that you have developer points when you make your reservation. They have to book them using a different system. Because of this you will not get a confirmation number right away. They will mail it to you and you should get it within 7-10 business days.
Hope this helps.