If the m/c takes more than 10 pound for a board then it is more than often dead. However, when you force a red, it does it's 'dead' patch right in the middle of forcing. Thats why when you play a SA etc you have to play for at least 3 boards to see if its during a streak or not.
And more times than not it isnt streaking and those three boards can cost upto on average £15. sometimes i think is it all worth it. depends who comes out up or down though really dosent it. atei in the morning!!!