Oldairhead 

Well, in ideal conditions I can replace a tube in a normal tire in about 5 minutes from dismount to remount. That includes disassembly, accessing the tools, the repair, repacking the gear and reassembly. If it is a tubeless system and I have a flat I have to first identify if it a puncture that wont seal, a valve issue, a liner issue or a sealant problem. There is no quick and clean fix if you have to put a tube in a tubeless system. EVERYTHING is more difficult and takes longer that it would otherwise. I have struggled through this a couple of times personally and it really sucked! If you are on a gravel road shoulder then keeping it all clean also takes extra time. If it is dark then you can double the time required, if it is raining then double it again, if you are 20 hours into your ride, cold and hungry then it can become nearly impossible! These things nearly always happen when it is least convenient so you can count on that.

I know of several other randos who also tried tubeless and went back to tubes. They decided like myself that even though there may be fewer flats with tubeless, when they did have a problem it was a lot more time consuming to deal with than compared to a standard tire and tube system. Perhaps it is the regions in which I often ride, which can be far removed from any services and even cellular signal, but I want to know that I can make a repair and get back under way. This is just a personal choice and not a judgement of others who choose differently. Just be prepared for the unlikely circumstances or accept the DNF!