I bought the TireGard monitor despite the warnings on the possible leakage since tje valve stem is held open. This was last July and I still have not convinced the manufacturer that they should not operate the way they do for me. I plan to write a review here on my frustrations but will summarize it here:The monitor usally reads the last updated pressure for a couple of hours to a couple of days to a couple of weeks. It seems to randomly update and often it is only one of the tires (sometimes front, sometimes rear, rarely both). The manufacturer says that "that is how they work, they do not update until the pressure changes enough". I said that, upon warming up for a few miles, the pressure should change 3-4 psi in the positive direction. They said that that may not be enough for an update but argued whether the tire pressure really changed upon riding unless I verified with a gauge. It is great when the temperature changed changed this spring to check the temperature using the TireGard: The TireGard said the tires were still the 35 degrees from February but, when I left the house, it was 65 degrees (air conditioned tires?). Further, the monitor is designed to turn off on its own after 20 minutes of no signal from the tire sensors. What that means in practice is, if the tire pressures are not changing "enough" every twenty minutes, the monitor turns off. I was finally on a long trip and had to turn the monitor on most every 20 minutes. If you do not notice that it turned off when you hit that nail, tough luck. Before you all blast me, I really think that my monitor is defective but I have already spent money to send it back once and all they did was replace the sensors. I want to be sure I know what they will do before I spend another $15 to send it back.
On another note, my first set of sensors did seem to leak, but the replacements do not seem to (except when I take them off since the TireGard had not updated for two weeks). It is possible that they are sensitive to how tight you put them on (instructions say something like "not too tight").