i'm sure it has worked for some people. you would definitely want to book at
exactly 7 months out (or at least get on the waitlist then) to minimize your chances of getting locked out of wdw.
the risks are:
1) you
will pay higher annual dues at a coastal
DVC resort (and over time this will offset the lower price paid upfront.)
2) you might wind up with even higher dues or a special assessment should a storm hit the resort (storm damage might also impair your ability to trade your pts for wdw resorts).
3) if you decide to sell your DVC, the coastal resorts will hold less of their value than the wdw resorts
4) you may get locked out of wdw at the 7 month window - it can happen - especially if you want to travel at peak demand periods like early december. this might happen very rarely...but if it frustrates 1 vacation out of 6, would it still be worthwhile to you?
5) there is a tiny chance that DVC might eventually decide to spin off some of their resorts - in which case, the coastal resorts would be the first to go.
but as long as you know the risks, you can decide if the upfront savings are worthwhile to you. most of the experienced DVCers here would advise you against it unless you usually intend to use the pts at HH or VB. but if you're feeling lucky, go for it.