I've had my Lifespan 4000i for over 2 years and have logged a little over 2000 miles without a hiccup. I have run on club treadmills that were much louder and less study than this unit. the only thing I have done to maintain this unit is mist some silicon on the back side of the belt after I fold it up about every month or so. I noticed the guy who gave this unit 1 star based on running shoes causing him to get shocked, I've never had an issue. It could be a grounding issue with his house or that fact he's using a power surge strip.