[twindman]

I also use the 507 non-flowthru valves.
I went for 9 years without them. But when at the Goshen Rally in 2014, my wife and I went on a geneology excursion (without trailer). We were about 2 miles out of a small town and my dash console came up with a tire pressure warning - down to 45 lbs or something. Got out to check it and it was down to around 41-42. Drove in to town to a gas station and started adding air and it was down to 30 when I started and 25 after a minute or 2. Jump in truck and drove down street to tire repair place a mile away and tire was at 20 or so. Had a split sidewall.
Replace tire and on the way.
Without a tps I would have been in the country changing my tire. And I DON'T want to do that with the trailer or have it blow out.