I believe its 12 months.
But theres always the chance of the account itself being disabled for abuse - which is something that can happen for using a bad IP address or any other reason they deem appropriate.
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AGED SUPER HIGH LIMIT ACCOUNTS: 10,000/$1,000,000 and 25,000/$500,000
Yeah I was planning on it, I'm thinking a binder with account details and labels on the phones are there any services that don't expire as often as tracfone?