We are close to the same formula. I use: Buy-in + Yearly dues divided by the total number of nights from my first stay until now. Example: Buy in 20,000 + 1000 (2008 maint) divided by 16 (Number of nights stayed in 2008) = $1,312.50 per night. But then the next year: Buy in 20,000 + 1,000 (2008...