The number of points that comfortable for you will be very dependent on your personal preferences, your financial status, etc. No one here can really tell you what's the 'right' amount. It's different for everybody.
Your best bet would be to look at the
point charts and compare them to your typical vacations and see how they match up. You can compare between resorts, between different dates.
Feel free to download my
DVC-Planner program. One of it's features is you can put in the dates for a vacation, and with one click see how many points it would take for that vacation in every combination of DVC-Resort and Room Type there is, being shown in a table display. (See link in signature below. The table display screen shows in the animated gif image as the one with the mostly yellow background)
Dues do go up annually, based on actual expenses. The DVC executive board has a fiduciary responsibility, so any increases in dues can only be for actual increases in expenses. You'll see that in the past dues have been pretty consistent with inflation. In the early days of OKW, on a couple of years dues actually went down.
Keep in mind that an increase in dues is still better than paying an increase on a hotel room. For example, mid season, a Studio at OKW weekdays is 10 points, and if dues were about $4/point, that's equivalent to $40. If dues went up 3% the next year, that's an increase of 12-cents/point, or an increase of $1.20 per night for that same room. Compare that to a hotel room of $150/night. If it goes up 3% the next year, along with inflation, it goes up $4.50/night to $154.50/night. That's an increase of 375% more than the DVC increase. This is where membership really pays off in the long run.
At 3% annual inflation, after 20 years DVC dues would be about $7.22/point, so that 10 point/night room requires $72.22 worth of 'dues'.
The $150/night hotel, after 20 years of 3% inflation, increases to $271/night.
DVC net increase = $32.22
Hotel net increase = $121.00
If you figure the difference between the DVC dues payments and equivalent hotel prices, multiply by how many nights you stay each year, and basically apply that ever increasing difference toward your initial purchase costs, you'll find that after about 5-8 years it's all even. After that date, you're staying for the cost of the dues along.
Of course, the beauty is that you don't have to stay in a DVC-Studio. In that case you don't compare costs as much as you compare lifestyle. What's the 'value' of staying in a 2-B/R DVC unit, compared to paying the same amount for a regular hotel room.