falsepretense

For a slowplay to be correct there is 5 criteria that have to be met. 1 Your hand must be very strong.2 You will probably chase everyone out by betting, but have a good chance of winning a large pot if you check.3 The free card that you are giving has good possibilities of making second best hands.4 The free card you are giving has little chance of making a better hand, or even little chance to give someone a draw to a better hand with the correct odds to call.5 The pot must not yet be very large.

I'm reading David Sklansy's book right now Hold'em Poker for Advanced Players, and my question is about the "strategic concepts" portion of the book. I think I have a good grasp on how to semibluff and how to try to buy the free card, but my question is this. Are these plays that should be used very often, or only occasionally. For instance, if it checks to me on the flop and I have four to a flush or and open ended straight draw, is it always appropriate to bet, assuming that there is a chance that all players will fold and that there is a chance I've just bought a free river card? Similarly,