CWSWine, it sounds like you are right on the verge of maximum distance range (without a repeater) on your rig. Unfortunately, there is really no good way to determine just when you are on that verge.
We hashed this same thing out a few months ago and at that time, this is what I found out about receiver/monitor readings straight from TST...
1. As long as all transmitters are paired (within range) with the receiver/monitor, you will receive updated data (or an alarm if necessary) from each of them, every few seconds.
2. If any of the transmitters fails to communicate with the receiver/monitor (falls off, battery goes dead, wheel flies off) during which time, any of the other transmitters are still communicating, you will receive an immediate alarm.
3. If you simply unhook and drive away from ALL transmitters (completely unpair)... the data will remain on the screen (unchanged of course) for approximately one hour and then an alarm will sound letting you know it hasn't received ANY data for that time.
I did not go into any detail here about the alarms/data if you have a tire that goes out of the pre-set parameters as you seem to know/understand that part.
I suggest you invest in the repeater.
2016 Flagstaff 8529IKBS Diamond Package 5th Wheel
Ford F-Series SCREW 4x4
TST Tire Monitor - Sinemate 3500w Gen.
2016 Nights Camped = 42