I count them out exactly every morning. 1 - 2 - 3 - 4 - 5. I've found that that is the perfect number for a 32 oz drink. 6 and the drink gets too watery by the time I'm done with it. 4 or less and it gets warm too soon. This was derived at over many many years of drinking a 32 oz coke in a cup with ice and a straw every morning on my way to work. I've now given up the Coke, but find that 5 is still the perfect number for whatever drink I finally decide to settle on.

Although, if I make sun tea, when I first bring it in I usually have to use the whole tray to cool it off .