Never seen a defrost cycle on a chest freezer although I assume someone has made one. Using it as a Keezer you would not have any issues of frost as nothing is at freezing temps, so there is nothing to defrost. Most are manual defrost which means turning off and opening the drain plug.
If you're using a temp controller, it doesn't really matter. The temp controller acts as a defrost cycle - once it gets to a certain temp, it cuts the compressor. It'll never get cold enough for the actual defrost cycle to kick in.