How often do you bluff the river after opp checks behind on turn HU?

[partygirluk]

I NEVER do this and I am think I am missing out on some serious EV. My thinking is that I am an aggresive player and my opponent will be expecting a river bet after he checks behind on the turn. However, after I check behind on the turn I find my opponent betting the river a LOT, so much so that a fair few of the bets must be bluffs. Most of the time I will fold as I have F all, but some of the time my F all will beat the opponents F all and I will make an incorrect fold. In mid/high short games, esp. in steal situations both guys often have such shite that perhaps it is worth bluffing the river some in this situation? 1 thing to note is that I have seen people checking behind on the turn with strong made hands (2 pair +) a fair bit recently (I think it is a pretty dumb strategy in most cases. Often I was plannning to c.r the turn and they could have got 4 BBs from me. However, they check behind and raise me on the river. I call because they either have a monster of nothing. Hence they only get 2 BBs from me.)