Join Date: Jul 2011
Location: Cincinnati, Ohio, USA
I've plugged 9 out of 10 of my last sets of tires. I'd bet I've got 60,000 to 70,000 miles on plugs and trust them completely. That being said, I'm religious about checking/maintaining air pressure.
I had one worm fail, but it was due to the size of the hole not the worm, picked up a huge barb wire. When it failed, I stuffed another one in and rode it till I had time to replace the tire.
Keep in mind when they fail, you get a slow air leak, once enough air has leaked out the bike handles differently so you'll know you've got a leak. If you keep running on the tire with low pressure, it will begin to heat up significantly.