If you cancel 31+ days out, points are returned to your account with no penalty. HOWEVER the points must still be used or banked by the end of the Use Year. If you are past the banking deadline, that is no longer an option.
For example, let's illustrate using a February Use Year. Points are always valid for stays between 2/1 and the following 1/31.
Assume you have a trip planned for August 1, 2013 arrival. The deadline for canceling without penalty is July 1, 2013. You would then have until January 1, 2014 to make alternate plans with the points. The banking deadline for a February Use Year is September 30. So, if you decided that you could not use the points by 1/31/14, any current year points from the 2013 Use Year could be banked into the 2014 Use Year.
If you cancel on less than 31 days notice, the points go into what is called a Holding Account. Those points can only be used to book a stay
60 days or fewer prior to the desired arrival. Success can vary greatly depending upon how popular the dates are among other members. Holding points cannot be banked and will expire at the end of the Use Year if not used.
It may sound a bit complicated to grasp at first but it's not too hard to understand once you own a specific Use Year.
I don't know if you're asking about cancellation because you are just covering all bases or because it's a frequent occurrence for your family. Generally speaking, timeshares are not a good match for people with volatile travel habits. If cancellations are commonplace due to job situation, health of a family member or other issues, you will find yourself losing points at times due to the restrictions which apply.
Travel insurance is offered which may apply if the cancellation is health or weather related. But you'll pay for the insurance. It comes down to a philosophical decision as to whether it makes more sense to pay for insurance or assume that risk, knowing that you may lose points someday.
We've been members for nearly 10 years--taking 2-3 trips per year--and haven't yet lost a single point due to a cancellation. In fact, we've never had a cancellation. (knock wood)