That's not been my experience of them. While they're not for every situation, and definitely not for safety critical fastenings, I've found them very useful for

That's not been my experience of them. While they're not for every situation, and definitely not for safety critical fastenings, I've found them very useful for many things in rally cars, all of which were extensively used in gravel rallies (up to WRC level), and never had any issues with loosening. They need to be installed with a decent tool though. Mine only cost about £50, and was a revelation compared to other jury-rigged methods!