Technically, you're supposed to take 20 hrs of credits throughout the 2 years that you are certified before it gets renewed. And since you are probably working in a pharmacy, your knowledge should be maintained sharp. As long as you don't let your certification expire out without renewal, I think longevity is better, but only marginally. Having a certification is only a marginal advantage, so having a marginal advantage of a marginal advantage is.... marginal.