The 150 points you banked from 2002 will have to be used in 2003, or else you'll lose it. So in June 2003, you'll have 300 total (150 from 02, 150 from 03). I dont' think you can carry that 150 from 02 to 04.
What you can do though, is to bank 150 from 2003 into 2004, and then borrow 150 from 2005. That is, in June 2004, you'll have 150 from 03, 150 from 04 and 150 from 05. 450 total.
That's my understanding.... please correct me if I'm wrong.
As for reserving for other resorts than your home... I never have a problem. Depends on what kinda room you want, and when you're going. Xmas week and/or grand villa will be tough. Otherwise, you should be able to get what you want.
We have 155 points (BWV), since 1997. We never have a problem reserving studio / 1 / 2 bedrooms 6 months ahead. We did a 2-bdrm during winter break (Feb) in BWV, then another 2-rm in May in HH, a 2-rm in BCV in Aug, 1-rm in BWV and studio in OKW. Studio is not that difficult for me, esp in OKW. 1-bedroom is tougher for some reason. Planning is the key.
If you can afford 150 points, go for it. It's the best impulse buy I ever did in my life.
DVC gave me a chance to treat my family for reunion, great hotel, services...etc. I wouldn't be able to afford BWV otherwise.