For a guy who claims to be skeptical of studies, I sure read about a lot of them. This one caught my eye though because it's an indirect endorsement of the concept of strengths.

Researchers at UC Riverside turned up some surprising findings in a longitudinal study of human longevity. Turns out the most cheerful people with the best senses of humor in their youth lived shorter lives than those who were a bit more taciturn and serious: "we found that as a general life-orientation, too much of a sense that 'everything will be just fine' can be dangerous because it can lead one to be careless about things that are important to health and long life." 

Well, darn. So much for a relaxed and happy attitude. But here's the real kicker: "'Don't work too hard, don't stress,' doesn't work as advice for good health and long life.... [S]ubjects who were the most involved and committed to their jobs did the best. Continually productive men and women lived much longer than their more laid-back comrades." 

Okay, so they're not quite exactly saying that playing to your strengths means you'll live longer. But if you read between the lines, it's pretty clear. After all, who's most likely to be committed to a job? Someone who loves what they do, or someone who hates it? 

So don't feel guilty if you love your work too much. Chances are it means you'll be around for a long time. I still think you should take some time for joking around, though.