Agreed; when I was an SL7 I thought below was a good estimation:
<=8 Innings - great game
9 - 12 Innings - very good game
13 - 16 Innings - average game
16 - 20 Innings - OK game
> 20 Innings - bad game
This might be too good for APA 9-ball at the 12 inning or less for an SL7, but I'd agree if it was 8-ball. But, I'm just hand-waving.
But, I can say that when I was playing APA 9-ball, I thought that if I went over 20 innings, I was having an awful game. Which was probably half the time.