You did right. Can't repair a cut and not fear the tire from then on. Price was right too! Why did your co-worker change tires at 400 miles? Dunlop to Metzlers or something like that?
I ask him the same thing! he said that he has had to many bad tires from Dunlop. He had them on 2 other bikes in the past and had 2 blowouts with in a 4 month time frame so he went to metzlers. He has used those tires ever since.