Since we are buying 170 points at the end of the month, can we, lets say in 10 years, bump the points up to 200 or 225 with out having to purchase from another resort if our home resort is sold out?
Once a resort is sold out, DVC will have no more points to sell for an add-on. Your options will be to find a resale for an add-on, add points at another resort or get on a DVC waitlist to see if they should reclaim any points for your use year.
DVC doesn't just "hold" extra points in case a member wants to add on later.