I wouldn't equate time off for boards with success rates. Houston (until this year) as well as Salus gave lots of time off for boards, and each of their board scores fell significantly within the past 3-4 years. Houston and Salus have both restructured since then. We'll see what this year's are like.
Berkeley and Ohio State offer little to no time off (3-5 days max), but each of them has significantly higher pass rates. I wouldn't consider time off to study a factor. I'd consider the education and matriculating student population a factor.