Is This A Leak Or Standard?

[mjm]

$33 Stars Blinds 50/100, 7 Players, Hero approx 3000, Villan approx 3500.

Dealt to Hero AK

Villan UTG raise to 200
Hero calls mid-position.
All others fold.

Flop A,Q,7, Rainbow

Villan checks,Hero 275, Villan Calls.

Turn 4 (completes rainbow)

Villan checks, Hero 400, Villan Calls.

River 8

Villan checks, Hero?

My tendency is to check behind here, thinking that a caller will be beating tptk and hating a re-raise...

Is this standard or a bit weas, as villan has shown no strength throughout the hand?