You should contact the resale agent that you are buying the points from and ask them to supply you with a printout from MS as to the history of current available/banked/borrowed points. I did this with my agent (Jaki at ATimeshare) and she was more than happy to help me out. It is an important step that I think many people forget to ask about. Also, unless you know the member number and have permission from the member, MS will not give you the information anyway (or at least this is what I have been told).
I just mailed my P & S agreement back to The Timeshare Store yesterday. My contract clearly stated all points for 2003 and then all points for 2004 and every year after............