Also depends on how strong yu think your original position is.
Guys that say they habitually buy back those half point sides (usually after the game is over) have far more losers than winners trust me. Even guys that take shots on middles with 3-4 points (in football) usually are buying off a stronger position and buying back on a weaker one.
I am all about the grind, and the safe money. But unless you are trying to middle a lot of games, or are buying back a lot of games your odds and theoretical probabilities aren't going to be equal. Especially if you are spot playing.
What might have a theoretical 15% chance to hit, doesn't necessarilly mean you have a 1 in 7 chance of being a winner. No matter whatthe math says. There is an OUTSIDE influence on that move, and trust me, sometimes that outside infuence is more than enough to sway the math.
You could have a time(set of numbers) where there are 20 examples. 3 of the 20 hit in the middle. But those 3 eaxample were also games where the fix was in, and the ORIGINAL number was BEATEN 100% of the time. The other 17 times were either coincidence, or a fluke. But they DID NOT hit the middle.
Very hard to use precdictive stuff to figure that out. Me personally I would have rather bet the 3 games I KNEW where in the bag and keep my original position, than buying back willy nilly HOPING to get something extra out of it.