I was recently contacted by a past client who was getting ready to purchase a new home and needed to access his documents from the sale of his home several years back. I normally do not keep files for more than about 3 years, so I could not help him out. Fortunately, he was able to retrieve most of the documents he needed, but he had to really search for them.
Moral of the story is that you never know what paperwork you will need and when from the sale or purchase of your home. Best to hang on to it for as long as you can. Scan the documents and put them on a disc or store them in the cloud, but make sure they are secure. Or ask your agent to provide you with a copy of the documents on a CD at the end of the transaction.