A couple of things to consider. If I keep buying bowling balls and my average is going up, good thing. If I keep buying bowling balls and my average is declining, its a bad thing.
If you bowl in a league where you are confident that the conditions are the same week in and week out, then maybe three bowling balls are fine.
If you bowl in one of my houses, you have no clue what the shot is going to be. Its suppose to be a rather high scoring house shot. Sometimes it is. If they have a touranment during the day, (Sunday night league), and they use a tournament shot, first the lane guy doesn't even know what shot it is, and then there is a possibility he will do a fill shot over the tournament pattern, not do a fill shot over the tournament pattern, do a fill pattern over the days shot or not do a fill shot over the days pattern. I found this out when I was new to the league and after three weeks of a fill shot over a THS shot, we got a tournament shot that had two squads of women bowlers on it, 4 women to a lane and the second squad got off so late they didn't even do the fill shot. So now I have to make sure that I have a varity of bowling balls in my bag when I go there on sunday nights.
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Nicanor (Ten On The Deck)