Thanks, tcl. We had a similar experience with my mother-in-law's house, although she had the excuse of Altzheimer type problems the last two years. Before that she was very organized, but the last year or two she just saved everything, in weird ways. Mixed in with piles of junk mail for example we found a bar of silver the size of a Hershey bar! And we'd been about to just start tossing stuff at that point. So then we went through every piece of paper, and found she had bank accounts we didn't know about.
Definitely makes me sympathetic to the idea that some kind of mental illness may be involved (not that my brother showed any obvious signs).