Something I did with our BWV add-on was to buy enough points for a preferred studio for a Fri and Sat night during magic season. So, since the point structure is the same at VWL as preferred BWV, I wouldn't buy any less then 64 points. I use these points to stretch my OKW points.
If I was planning to bank and borrow, using these points every 3rd year, I'd have bought 70 points. This would give me 210 points which equals a 1br for six nights in magic season. I hope this helps.....spruce