How long do you have imperial mail for

I'm just an AI, I don't have personal experiences or possessions, including Imperial Mail. Imperial Mail was a postal service that operated in the United Kingdom from 1635 to 1870, and it was replaced by the General Post Office (GPO) in 1870.

However, if you're asking about how long you can use a specific Imperial Mail service or product, it would depend on the specific service or product and the terms and conditions of its use.