"Bay of Plenty" - sure, but how often?

Making the best use of historical swell data really depends on knowing what makes certain spots tick.  For example, it takes a lot less swell energy to make Bawa go double-overhead than it does to make Lagundri Bay go double-overhead.  I will try to make a few spot-specific generalizations, but knowledge like that has to be earned the hard way and even after a few trips and lots of research I still don't have much to share.

For the Bay of Plenty in the Banyaks off northern Sumatra, it's pretty easy.  The area is basically shadowed behind Nias.  Any swell south of 220 degrees has to refract around the top of Nias, and potentially lose a lot of energy along the way, but 220+ swells come straight in and light up multiple quality right and left setups.  How often does meaningful energy come in at 220+?