I've been trying this trick for a couple of months but I haven't done it enough to see what the long-term effects would be. So YMMV.
You can pick up lot of different air fresheners for the car at stores and the local car wash. When the smell is gone I use them to quiet battery rattle. I just cut pieces to the size a light will take.
Some are fresheners that are in jell form that never dry out even in the hottest weather. Some are felt pad and some are made of cork. I try them all and see what works best to keep batteries quiet.
I rather like the jelly freshener. It is sticky and will stay at the bottom of the light but will pull out without leaving a sticky residue in the bottom of the light. With the jell freshener it can sometimes be a Goncz to get the battery out; it is sticky. But the battery will, with a couple of shakes, always come out.
A nice off-shoot of air freshener is when I change batteries the light has a nice smell and never has any (flashlight) body order. /ubbthreads/images/graemlins/smile.gif