...we normally would stay at a moderate resort (almost always during Easter break)... I also wonder if at a certain point (10 to 15 years?), my family would get tired of going to WDW every year.
Is yours a family of 3 or 4, who would be able to fit in a DVC studio unit or would you have to book 2BRs? The DVC resorts are lovely resorts. Would they please your family or do you want to stay at non-DVC resorts, for more variety? Do you always stay onsite?
According to the Disney website, if you planned to stay during Christmas week 2003 (similar to prime holiday Eastertime), a rack rate, 7-night stay at a moderate resort would be $1,436 including all taxes. Multiplied by 10-15 years, this is $14,360-$21,540.
The DVC points required for the same stay in a studio at OKW would be 147. 150 points at OKW cost about $10,500 resale plus annual dues of about $523. 10-15 years of membership would cost about $15,730-$18,345.
The DVC points required for the same stay in a studio at any other WDW DVC resort would be ~181. 180 points at BCV from DVC costs about $15,120 plus annual dues of about $715. 10-15 years of membership would cost about $22,270-$25,845.
Those are the two extremes of what DVC would cost. If you then sold, whatever amount of money you received would be deducted from your total costs. This is a very simplistic way of looking at the figures.
Some will look at the numbers and say it's cheaper and easier to book for cash, hope for discounts, have complete flexibility in year-to-year planning, invest the purchase money elsewhere and not have to worry about taking out a purchase loan, adding interest payments to the above. Others will say they would expect to see a large portion of their purchase money return to them, making it worthwhile. What you may need to decide is... is it worth tying up (and possibly losing some of) your upfront purchase money for the perceived benefits of DVC membership? For some folks, the answer is a resounding yes!, for others no! and for many, it takes more consideration. HTH.