I have always been a big fan of natural carbonation, but would like to experiment with force carbonation in kegs. I have noticed that most carbonation charts list PSI and Temp to achieve desired CO2 volumes, but I see nothing describing over what time period they are suggesting to leave the keg connected at pressure. The Carbonation Tool in the Beer Smith Software gives no mention to a scale of time. Is there a standard amount of time that you want the keg attached to the gas per amount of pressure/temperature? 12 hours? 24 hours?