Both of these images were taken with the camera on a tripod with MLU and the in camera timer. The top photo with the IS off and the bottom one with IS on. I took dozens of pictures at this setting. The first four with the IS on. Then I noticed that the the first four photos were not sharp and I could see kind of a crescent shaped movement of the lights. I turned off the IS and took a few dozen more shots that were sharp with no crescent shaped lights.

There was a very light breeze and the tripod was setting on a lawn. It is possible that the wind set off the IS and caused it to hunt but in this case is was clear that for the best results the IS had to be turned off. If there was any movement caused by the wind, in was not noted in the final pictures but the IS hunting was very noticeable.

The moral of the story, for best results with longer exposures, turn off the IS when the camera in on a tripod.