5/10 NL live two pair OOP on monotone flop

[McStinky]

Foxwoods 5/10, 10-handed.

Haven't played with villain very long but he seems decent, probably sees me as decent too.

Villain has 2000, I cover.

I am in SB with T[img]/images/graemlins/diamond.gif[/img]5[img]/images/graemlins/diamond.gif[/img].

Preflop
All fold to villain on the button and he limps in. I complete and BB checks.

Flop (35): T[img]/images/graemlins/spade.gif[/img]7[img]/images/graemlins/spade.gif[/img]5[img]/images/graemlins/spade.gif[/img]
I lead out for 25, BB folds, and villain raises to 75. I call.

Turn (185): 3[img]/images/graemlins/club.gif[/img]
I bet 125. Seemed like a good idea at the time. He calls.

River (435): 4[img]/images/graemlins/club.gif[/img]
I check. Villain thinks for quite a while and bets 275. Should I be folding here because he could have a busted spade draw but not enough? Does the long pause before he bets make a bluff a lot less likely? But how many hands could he be valubetting here?