My Raleigh Passage Hybrid has 4 year old Schwalbe Marathon Pluses on it. All I've had to do is check the air every week or so and ride it. Anyway, my other bike, an mtb, is out of commission. There is a 10 mile dirt track loop I like to ride. I reduced the pressure in the Schwalbes from 95 to 60 lbs and hit the path. I was cruising a smooth straight-a-way when all at once my front wheel went out from under me and I went over the bars. It was like the front wheel hit an immoveable object. My side, shoulder and face hit the ground in a cloud of dust. After I gathered my wits and found out I was ok I prepared to fix the bike and ride home. That's when I discovered I had left my pump at home. I never do that!
I walked 4.5 miles in the 100 degree heat, then my neighbor gave me a lift the last 1/2 mile.
Upon inspection I found that the stem had broken off the tube. I've never had a flat with those tires. It looks like the tubes wore out before the tires did. Just to be safe I replaced the rear tube also. I'm always careful not to stress the stem on a bike tire but I think this one just cracked from normal use. I glad I didn't break my collarbone. I broke the other one 4 years ago. I could have had matching scars.