I've been pluggin my tyres for years, ever since I first started as a motorcycle courier.
If memory serves me, 1 rear tyre when it was finally worn out had 4 plugs in it, or was it 5.
Best $40 I ever spent, has got me out of the pooh many times, and I have never had 1 let me down. Even Die hards "Ill never use a plug" when faced with a very long wait for a lift home and a huge towing fee, seem happy for me to pull out the emergency pump and plugs. Funny bout that, funny how they all go out and buy there own too.