Let's say a permanent neodymium magnet is used to suspend an iron weight from a ceiling, as crudely depicted here:
Does the magnet gradually lose strength and eventually drop the weight, or will the weight stay suspended forever? If the latter case, wouldn't that be a violation of conservation of energy, in that it should take a certain amount of force to keep the weight suspended against gravity, and the energy to do that has to come from somewhere? And also in that case, would it make any difference if instead of leaving the static load on the magnet, the weight is instead repeatedly detached and then gradually brought towards the magnet from below until it 'jumps' up to contact the ceiling (presumably making the weight travel upwards expends some energy, from somewhere)?
I suppose the underlying question is, if a permanent magnet is used to do work, where does the energy involved come from and can it be exhausted?