I think because it could does not mean it always does react. It is just advice. Sometimes for whatever reason I didnt have time to do the 24hour warm up and I found more often than not the sensor was accurate as soon as the activation time ended. I suspect it is complex and largely individual. I am pretty sure in my calls abbott did not advocate the 24 hour thing. Though they did advocate applying skin-tac-wipe to stop them dropping off which was my biggest problem. Putting aside the inaccuracy you have - aren't they fantastic for measuring the rise and fall - PMP at 2 hour - impact of exercise at the time and after. Showers, DP the list goes on - really informative.