re: Poker & Problem with limpers
It's not a problem when opponents who are behind call your raises after limping in. Yes, they'll draw out on you, and the more of them there are, the more often one of them will draw out.
But the goal is to win as much money as possible, not the largest number of hands. Assuming you develop some ability not to pay off to the max when opponents hit their hands, it's profitable to play opponents who are willing to let you build pots while they're behind.