Engine Stop Troubles

Please i need some help i have a 2002 kawasaki kdx. I have bought 2 engine stop buttons now. The original was fine and lasted a good long while but it went out so i got a new one. It only lasted a month so i bought another and now its doing the same a litle over a month later.... any ideas or ways to fix this problem?????? it seems that they work fine but then they slowly stop working and now it only works once every 15 rides.... Please help me out.....