Dunlop's guidelines specify a puncture no more than 1/4 inch in diameter, in the tread area, may be repaired using an inside patch suitable for the tire construction (radial or bias). After the repair, the tire should be closely watched for blistering or knots, which would indicate significant internal damage, for the first one hundred miles, and the tire should be considered limited to 75 mph continuous operation after that. Realistically, I won't repair anything that I would consider to be unsafe, so the puncture needs to be reasonably clean, in the center 60% or so of the tread, and no evidence of broken carcass cords on the inside of the tire when we dismount and inspect it. I personally have run a properly repaired tire for more than 9000 miles on my own bike, with no discernible effect on life or performance.