in my work I find a lot of old lids,im a dumster/skip truck driver,ive never kept any but ive destroyed a lot!ive placed them under the stabiliser legs/feet and have had a good crush at them,mostly they lift the truck up on an angle before they show any sign of letting go either with top or side loading,once they do its only by a margin they don't collapse,this aint no proper technical test but they take a lot to break the shell,i think the inside foam ages?and might be less absorbent to impact?i call bull#$%* on the painting or stickers or even drilling of lids makes them weaker!