Last year, i was in a bit of a slump. After cleaning at home, i happened upon my old Black Widow Pearl and decided to take it to leagues to play with. This is the only ball i have shot 700's with. I've been close with others, but not gotten there. The first 4 weeks i used it last spring were amazing, including another 700 and 3 high 600's. I also used it in a tournament in my local house, and seeded 3rd of 65+ bowlers rolling another 700, and with the match play added in, i shot 2 700's with it on the day, and finished 2nd in the tournament to my 233 average teammate.
I've been told a theory on why balls do this, and it's because the oil in the coverstock that used to bog the reaction down has since migrated further into the ball leaving yourself a fresher surface for a little while.