Bill , I have two sheets of "Chrome" BMF that I've had just over one year , one came with a few wrinkles in it and the other didn't have any . I've kept them laying flat in the envelope and in the refrigerator since day one and there are no additional winkles appearing . I just used some on a body yesterday and it worked just like the first time , nice and smooth and the adhesive was just fine . I've heard that the "Ultra Bright" Chrome is a bit different but I've never tried it . I always polish the "Chrome" before cutting it from the sheet to give it a bright finish ! Also I've experimented with some of the wrinkled stuff and was able to smooth them out while applying the foil with no cracking . When I was finished it was impossible to tell it had ever been wrinkled !
Maybe I've been lucky but this is my experience with BMF . I'm interested in how you make out with five year old sheets , please let us know .