This garage had 25 years worth of belongings stored in the most suitcases I have ever seen. It took a skip, which we filled and many bags to the charity shop over 3 separate visits working with a helper and the homeowner.
There is still a lot in here, but they can get to everything and will be asking their grown up children to take their things periodically.
This is a short synopsis of what I have learnt over the years as a professional organiser, especially with regards to hoarding clients and how to work with them.