I think the biggest issue with a tire plug/patch is the "what if" Without data, I can tell you that a plugged tire is prone to leak before an intact tire. You can argue it if you want to because I don't have any numerical proof to back that up. Logically speaking, however, a tire with a hole in it will leak before a tire without. Plugs will stop that leak, sometimes forever sometimes temporarily. Motorcycle tires are flexed much more than car tires so there is a greater risk of that plug being pushed to a position that is going to allow the tire to leak. So in the end, a plugged tire may hold air and last the rest of it's lifetime or it may not. As a rider, it's up to you to gamble your chances. I don't know of any deaths or serious accidents with blame to a plugged tire, but you are at a greater risk since that tire is damaged. Weigh the odds and do what you want to. Typically I won't ride much on a plugged tire and when I had my shop I definitely wouldn't plug a tire for someone because of the liability risk.