I used to wax my chains at @500 miles, but have since shortened it down to @200 miles simply because I enjoy waxing. I have 3-4 chains in rotation for each bike so I end up waxing at least every other week even though I don't need to. I have found over the last 5-6 years of waxing that my drive train and especially cassettes have lasted much longer. I blame this on the fact that I'm not running my drive train covered in oily sludge.