Chainrings are easy enough to inspect. That said, chainrings tend to last a long, long time - much longer than your cassette.
I love this kind of discussions. It reminds me how happy I am to be a singlespeed cyclist. My whole drivetrain lasts longer, and the rear cog which I seldom have to replace (steel singlespeed BMX cog, straight teeth) costs much less than a cassette.