I believe that I read somewhere that stone images in temples needed to be replaced every 3,000 years to be effective as the residence of a deity. This would mean that stone, like clay idols are temporary 'bodies' of a deity, but that there is simply a difference in time frame (clay idols generally housing a deity for about 10 days, for example.) Can any one point me to a reference which specifically talks about stone images and their duration as effective 'housing.' Either original or secondary sources are fine. thanks in advance