Mother died. I pay her medical bills. Medicare takes a long time to process. How long do I wait to close account and assume all bills are processed?.

You will need to speak to a Florida attorney about this. Normally, you cannot continue to spend from a person's account after they die.  If, however, you are a joint owner of the account, you now own it and can do as you please with the funds.  You may need to open an estate with her will, if she has one, or apply to be appointed ad an administrator.  It may help to call the county register of wills and ask about this.