I just wanted to expand on this a bit. Sponges are crap, they induce swirls because any left over dirt on the surface (normally that you can't even see) gets trapped between the sponge and the top coat. When you push the sponge around these tiny bits of dirt create the swirls. Swirls are tiny scratches in the top coat which reflect the light at different angles to the rest of the unscratched paint, this is why the scratches can be more obvious under certain types of light.
A wash mitt is designed to trap the dirt in its fibers instead, keeping them away from the paint to reduce the risk of inducing swirls. Some other stuff can also be done (such as the two bucket method, various pre-cleaners, eg, snow foam) to reduce the risk of the dirt in the first place and thus the likelihood of inducing swirl marks.
All that being said, swirls will always come back! It doesn't matter how good you are or how much care you take, they will always return, it is inevitable. If you follow a good routine you'll definitely reduce the frequency and depth of the swirls making them easier to remove. I'd honestly be surprised if you needed to fully machine polish a whole car more often than once every two years.