I have 4 sets of wheels set up tubeless and have been running them for a few years with no problems, they have punctured but sealed, never had to stop to repair them or put a tube in, I hadn't been out on the bike for over a week until today and when I took it down from its hanger the rear tyre was completely flat, so I pumped up the tyre and could hear hissing, I upended the bike spun the wheel up and liquid was spaying out of an hole in the centre of the tyre, it got less and less and eventually stopped, but there was a bit of metal sticking out of the tyre, I decided to pull it out.
It left a small hole and the tyre went down, I have had some plugs since going tubeless so I put one in and trimmed it of flush, pumped the tyre up and went for a 32 mile ride with no further problems, its the first plug I have used since going tubeless and was a lot easier than removing the wheel and tyre mending a puncture or fitting a new tube, of course I did this in the comfort of a warm garage, it could be a different story on a cold wet day outdoors.