Bob, no one can say for sure, but I would suspect that getting Spring break studio at 3-months would be very tough. At 8-months you would have a better chance. And even if it was full, a waitlist at 8-months would have a very good chance.
Remember, Spring Break and Christmas are the only two times of the year where
DVC resorts are in Premier season.
Premier, the highest season, for DVC
point charts is only 22 days per year, and 14 of those days are the week before and the week after Easter. (With Christmas being the remaining 8 days)
Also note that 7-days in premier season for a Studio at BCV requires 181 points so your 150 would not be enough.
If you did 6-days it's 138 points. (If only one weekend day, or 162 points if 4 weekdays and 2 weekend days) If you only do 5-days and make them all weekdays, it's 95 points.
For a BCV studio in premier season, weekdays are 19 pts/weekday night (Sun-Thur), and 43 points per weekend night.(Fri or Sat)
For comparison, in Adventure season, a Studio at BCV is 12 points/night weekdays, and 22 points/night weekends.
During high point periods such as Premier season, Studios seem to be more popular as people try to conserve points. Then they will get 1-B/R or 2B/R units during lower seasons. I for one am like this, getting only a Studio during high season (we go for New Year's Eve), and 1-B/R any other time.
For Example, probably biggest difference would be a 2-B/R at BCV, BWV (pref), or VWL during Premier season for 7-days (462 points), or getting a 2-B/R at OKW for 7-days during Adventure season (218 points).
For us, a Studio at VWL, BCV or BWV(pref) for 5-days (Sun-Thurs) in Premier season is 95 points. During Adventure season we can get a 1-B/R at OKW Sun-Thu for 80 points.
Post back if you have more questions.