I would say let peppers begin fruiting two weeks after being transplanted. However, I have had the occasional plant produce three or four and then stop while those mature. That's unusual, though. Most will keep producing from start to finish.
A lot depends on the individual plant. Two of my plants last year just kept fruiting and fruiting, right up to the end. I got 10 pounds, almost five dozen, Anaheim-type peppers from one of them. In some places, you couldn't see the leaves for the peppers. Another plant gave me three peppers and then stopped producing until those were maturing.
My Shepherd book recommends pinching baby peppers (not flowers) from a few plants while letting the others do their own thing. That way, you will be certain to have peppers all summer long.