Quote Originally Posted by BMbikerider View Post
It is probably down to the age of the lenses. Not so much the use they have but the grease they lubricate the helical threads with Too much and they are stiff, too little and they get sloppy. All it needs is a good service to get them back up to standard.
My experience is that the factory lube lasts a long time, but the looseness is definitely associated with usage. Use the lens more an dhte looser it gets faster. Maybe there is some issue with the amount of grease used, but there may be more of an issue with the shear strength; the grease comes in different "thicknesses".