Made nut flush when board paired...

[Doc7]

Villian is seeing 60% of flops and has never raised pre-flop in 30 hands so far. He hasn't ever raised on other streets either.

At what point on the river should I have just called his raises?

PokerStars 0.05/0.10 Hold'em (10 handed) converter

Preflop: Hero is UTG+2 with 3[img]/images/graemlins/diamond.gif[/img], A[img]/images/graemlins/diamond.gif[/img].
<font color="#666666">2 folds</font>, Hero calls, <font color="#666666">4 folds</font>, Button calls, <font color="#666666">1 fold</font>, BB checks.

Flop: (3.40 SB) 9[img]/images/graemlins/spade.gif[/img], K[img]/images/graemlins/diamond.gif[/img], 4[img]/images/graemlins/diamond.gif[/img] <font color="#0000FF">(3 players)</font>
BB checks, <font color="#CC3333">Hero bets</font>, Button calls, BB calls.

Turn: (3.20 BB) 5[img]/images/graemlins/club.gif[/img] <font color="#0000FF">(3 players)</font>
BB checks, <font color="#CC3333">Hero bets</font>, <font color="#CC3333">Button raises</font>, BB folds, <font color="#CC3333">Hero 3-bets</font>, Button calls.

River: (9.20 BB) 9[img]/images/graemlins/diamond.gif[/img] <font color="#0000FF">(2 players)</font>
<font color="#CC3333">Hero bets</font>, <font color="#CC3333">Button raises</font>, <font color="#CC3333">Hero 3-bets</font>, <font color="#CC3333">Button caps</font>, Hero calls.

Final Pot: 17.20 BB