Hi, Renessa,
DVC expires in January, 2042. Until then, each year, on the first of a specific month (known as your "use year"), your points renew.
For example, suppose you decide to purchase 250 points and your use year is February:
Every year on February 1st, you receive 250 points to use to make reservations. The points "expire" (i.e., you lose any unused points) on the following January 31 unless you bank them.
Banking them just means that you notify Member Services that you want to use them next year. (You can also borrow points from the next use year). There are limitations on the number of points you can bank depending on when you call to bank them. For example, you can bank up to 100% of your February use year points if you do it by the end of July. There are other rules and the "deadlines" depend on your use year.
The best place to get your questions answered is on the DVC Forum. There are lots of helpful DVC experts that frequent that board and you should get good information and good advice to help you make a decision.
Here's a link to that board:
http://www.disboards.com/forums/forumdisplay.php?s=&forumid=28