laydowns vs. unknown opponents

As we all know, the answer to nearly every HE question begins with "it depends on the opponent." But as we also know, we often don't have the information needed to classify a certain player. So we need to have some basic rules about how to play the unknown, or the little known, opponent. What I'm interested in is when to make a tough but fairly clear-cut laydown.


Example:


15/30 HE- limper from 2nd position, you raise from the cutoff with AdQd. BB calls, limper calls. Flop comes Q-T-4 rainbow, one diamond. BB checks, limper bets, you raise, BB folds, limper calls. You've only seen him play a couple of fairly straightforward hands so far.


The turn is the 9 of spades. He check-raises. Now he's clearly representing at least 2 pair, and you may be drawing dead.


Question 1: Assuming your play here has no effect on future EV one way or the other (let's say it's your last hand, and you're leaving town tomorrow), do you lay your hand down here?


Question 2: Assuming your play here might have a great deal of influence on future EV (let's say you're trapped on an island for a year, and you'll be playing thousands of hours vs. these players), does this change your decision at all on this hand?


I just hate putting in a bet on the turn, knowing I'll have to call the river, just to have him show me a set of nines or whatever. Even when he's semi-bluffing with QJ, I feel like I simply got lucky, instead of outplaying him.


Any general ideas about when to make a laydown vs. an unknown but seemingly sane opponent are welcome. Thanks.