How often do you replace your tweezers?

I've had mine for some time and I feel like they've lost they're grip in terms of when I attempt to pull out a hair sometimes. Is it just me or you actually replace them every so often?

Which kind do you use?

I buy the Revlon tweezers, they're just called slanted tip tweezers, no special name, from Walmart. They've been the best pair I've ever had.