This question is so subjective, and of course there is no proper answer. So many things influence how many points someone "needs":
- Are you going every year or every other year?
- How big is your usual group that goes with you? (I'm talking number, not size

)
- What resort do you want to own at, and what is its point schedule?
- Are you satisfied to stay in studios or do you insist on the luxury of a 1BR villa?
- What time of year (point schedule) do you want to vacation?
- How close to WDW do you live? Do you plan on multiple trips per year?
- Do you like to move out on weekends to save points?
- What can you afford to put into quality vacations?
I'm sure there are tons more variables, but just these allow for enough permutations to show that there are easily thousands of "perfect" point amounts.
I think HBC nailed it...it could be anywhere from a very low number to a really high number. Just make sure that the additional cost plus additional maintenance doesn't push some other important expense out of your budget.
