new spark plugs

Ok I have a 2003 mercury sable that needs new plugs. I bought them and the auto parts store guy told me not to adjust the gap even though they are gaped at .060. The car specs are .042 to .046. He says they will perform better and last longer if I leave them alone, if I adjust them I will distroy the platinum and they will burn out early. Has anyone heard about this or delt with it before? I would like to change the plugs as they need to be changed but I only want to do it once as the back three are a bear to get at.
thanks for any input.
cougarxr

If I were you I would go ahead and change them. If they don't work go back to the store and talk to the guy who gave you the plugs and told you that they would work. Just nicely tell them that you are unhappy with their service and you just want the right plugs.