EU said " And they had been there for quite some time "
EU, you shouldn't mix speculation about one thing (length of time) with information from a witness..
you have no data in that post that talks about length of time, other than in a speculative manner.. That's a complicated matter, and Brian is, by far, not qualified to offer any informed opinion other than their physical state when he found them.
edit: more specifically, regardless of their condition and any determination about weathering factors..the amount of time they were in that particular physical location can't be determined from available information.