I don't think there is a true answer to your question. I think most people would agree if you play a well dialed in machine and don't like it with in a few plays it is highly unlikely you will ever grow to like it. I also think it takes about 10 or 12 games to see if a machine has stay power in a smaller collection. But to say you can get an answer in "X" number of plays just isn't going to work.

One thing we have learned over the years is DON'T decide if you like a game or not if you are playing a machine that is not 100%. I can't tell you how many machines we bought as projects - played them a few times before we had them 100% - decided we didn't like the game - put it up for sale before we had it dialed in - sold it and then finished it before customer came to get it - and once it was working 100% and fully shopped we wished we could keep it.

Bottom line is to follow your instincts as long as you are playing a recently serviced machine. If you play it a few times and it doesn't seem to fit odds are you will never like it. Or if you play it a few times and love it chances are you will always enjoy it. I am not saying this is the case 100% of the time but odds are 90% of the time your first instinct will be correct.