We pondered the very same issue when trying to decide...a couple years ago when we were 45, 43, 16 and 10.
As you can see from my signature, we love Disney but were not sure how much we'd want to visit as the kids got older.
However, since we bought back in '06, we've taken (2)
DVC point trips (throw in a non-points
DCL cruise) and have (2) more DVC stays booked.
We also think we'll take at least a few WDW trips before our kids decide not to participate for a while.
When that time comes, we plan to use points on Adventures by Disney, exchange them out, take Disney trips w/o kids or rent out points we don't use.
One day, our kids will eventually come back around if/when they have families and the whole cycle will start over again.
It seems like (from the posts here) the luxury of owning DVC comes later in life. For us, we looked at buying long-term value not necessarily related to our current age or that of our kids. Rather, we looked at whether the system in place would mature with our travel needs.
Good luck with your decision.