About 4 or 5 years ago, I also noticed the teeth on my 9 speed ultegra chainrings were looking like shark fins. I bought new chainrings at the time and out of curiosity, I compared the brand new ones to the used ones. I held both rings next to each other under a large magnifying glass and the tooth profile looked identical so I cleaned the used ones up and put them back on. The new rings are still sitting in my toolbox awaiting the time when the used rings someday give me problems. I have at least 3 times more mileage on this bike than yours so I'd say you're worrying about nothing.