The "expert" at your Guitar Center probably never played an acoustic in his life. Tens are called "light" for a reason!

My 36-year-old Martin has never been strung with anything lighter than 13s, and it hasn't snapped in half yet. I've got arthritis in my fingers, sure, but I've spent many more hours of my adult life typing on keyboards than I have playing on the guitar fingerboard. And I still wouldn't think of going to flimsier strings; I just take my glucosamine, suck it up, and play hurt.