I do this once a day. Most annoying is that my Leica M8 will then do some TTL metering, and decide that 32 seconds is the proper exposure time... followed by a LOOOOOOOONG shutter, the ominously-missing second part of the shutter actuation... followed by 32 seconds of noise reduction.
Then I get a perfectly black image, with a few colorful pixels.
My subject has moved to Nebraska by this point.