General Turn Semibluff question?

[sevenhigh]

The game:

6 handed 100 bb deep everyone with full buyin

The hand:

Raised it up preflop in position get called by one limper...
flop comes with a decent draw (8+outs), opponent checks , hero c-bets, villain calls.

Turn is a blank, villain checks again.

What determines if ever you should bet this turn?

My general strategy is to take the free card. But recently people call all my c-bets with nothing and i hate bluffing at the river and getting called by k6 or whatever. Betting the turn takes it down very often. Downside is you can be check raised off the good draw.

Comments appreciated.