It will be 30 years this August that I've reloaded and have always cleaned by brass. When the brass is clean and shiny it is easier to locate cracks or blimishes which may cause an unwanted mishap (proactive and preventative measures), especially in the field miles aways from the nearest help or on the rifle range. Secondly, I definitley find that the cartridge cycles better in and out of the chamber when clean. I clean my brass after every shooting, it's the RCBS Vibratory cleaner (sits outside on the patio) that does all of the work while I sit back in my man cave and watch a hockey game.