When we were going through the debate about gear warning systems and how they should work for our amphib. there were lots of "What if . . . . . then it would not work" arguments. In the end my view on that was "If you wait for the perfect we will never have anything." In practice I did not come across a situation when it was not effective but of course that was no reason for lack of vigilance.
Practice is now to raise the gear after every land take off and, indeed, one of our members had a EFATO last week and landed straight ahead wheels up with just scrapes.