Mushroom plugs suck. Use a sticky string and it will last longer than the tire will. Some lawyer types will tell you how this is so wrong and all that. It's your prerogative.
Not to be wishy washy but now that I reflect further, if the tire has 6000 miles on it it's probably about shot anyway, so I would maybe lean more toward getting a new one unless you are in the middle of a trip or something.