These certainly transformed very quickly - so far, I don't actually think I've seen a confirmed slime mold on any of my moist chamber barks - this one, even though it looks slimy, is probably a fungus as well.
However, the question remains pertinent - the fruiting bodies of both slime molds and fungi can sometimes last for very long periods of time - with some species many many months. These guys are quite small and in a fairly controlled environment, so I would think there will be evidence of them on the bark for the foreseeable future.
RE: The Amateur Mycologist #35 - Update - Likely Licea variabilis Slimemold! Morphological Transformation Caught On Time Lapse - In Depth Analysis