We were lucky and started fulltiming long before we expected to be able to at retirement. We were also lucky that one of our sons had a heated/cooled basement room to store most of our boxes. He also got use of some of our furniture to repay him for storage space. Mainly because we weren't sure working and fulltiming would be what we wanted to do and it had taken years to accumulate some of our furniture.
8 years later, we've since whittled down to a few irreplaceable photo boxes, put all the old home movies on DVD's and given away much of what we will never use again. Three years ago, we set up our 'guest room' at our daughter's when we're only visiting for a weekend. She's now using the furniture and it's holding up quite well. Our guest room has a walk-in closet with the few remaining boxes we can't part with.