When to let go?

[Grease]

OK, Playing last night, I had two seperate instances where I had very strong river hands and value bet against one or two opponents. One time a scare card came, one time it didn't. Both times the opponents are fairly LP and I have yet to see any check/raising done by anyone at the table (other than myself, of course) I can't seem to get away from these hands, but should I want to? Do I want to make these laydowns, or is paying off the definite correct move here? Thanks guys, I hope to get some good responses. Where do you draw the line between paying off due to pot size and going with your read/gut feeling?

Hand 1:

I have AA in MP.

One limper to me, I raise, one cold-caller, limper calls.

Flop 356r

Check to me, I bet, both call.

Turn 9 completing rainbow

Check to me, I bet, cold caller folds, limper calls.

River J

Check, bet, raise, I...?

Limper was pretty LP, haven't seen him make a move yet, but I hadn't ruled out the possibility entirely.

Hand 2

I have KJo in MP. Two limpers to me, I limp, 2 more limp, SB limps, BB checks.

Flop Q109 two diamonds (I have K [img]/images/graemlins/diamond.gif[/img])

Check to me, I bet, one caller, button raises, folds to me, I make it 3, caller calls, button caps, I call.

Turn: 5 [img]/images/graemlins/club.gif[/img]

I bet, both call.

River: 4 [img]/images/graemlins/diamond.gif[/img]

I bet, one folder, button raises, I...?

Is this pure mathematics, or do great players have something else helping them here? I'll post some comments later, I don't want to give anything away.