M.S.
I could have written what you did my story is so close. My grandma would also save everything, including the plastic butter containers. She kept everything in piles and piles. But, she always kept places to sit on the couch, and paths in the house. Actually she would put everything in neat boxes. And then stack boxes on boxes on boxes all the way up to the ceiling. She would sometimes mark what was in them, but mostly she had "areas" for different things.
We never really classified it as a mental illness because she had lived through the Depression in North and South Dakota, where she lost her dad at like 8 and so her mom had to provide everything. She then had to swim out of the Vanport Flood and almost didnt' make it.
So, she lost everything twice. It just made sense that she would keep everything, but I have noticed hoarding tendencies in at least 2 of my aunts and mom, and even an odd attachment to some things.
But, I love to watch that show, and my husband hates it, which I think is so funny because he is really comfortable in clutter!