My husband and I will be the ones responsible when both of our parents pass, even though we both have siblings, we seem to be the most 'responsible'. I cringe when I visit my parent's basement, or my dad's machine shed. Literally, you cannot walk into it. My parents live on the farm that my grandfather purchased in the 1930s. My dad worked the farm with my grandfather. When g'pa passed away,at home at age 100, my parents moved into the family home, clearing out most of my grandparents things indoors, but there is still a lot of it in the attic, I believe.
My inlaws are a little better, but they have a farm with a very large home(packed to the gills) and a lake place with 2 storage barns. (we're talking huge pole buildings.)
We sincerely hope that our parents, both sets, live long enough to downsize and make decisions on their own 'treasures'.