Account Upgrade then Downgrade to Free

If I temporarily upgrade my account from a 10GB free account so as to be able to upload large files and then I downgrade my account, specifically back to a free account, what happens to the files stored on Box that are over the free-account size limit? After the downgrade, I would like these large files to remain stored under my 10GB free account (I will not come close to filling up the 10GB's) and be able to download them under the free account. Thank you all.