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This completely depends on where the avm is located, what symptoms it presents, and whether the avm is treated or not.
Treated avms have a good chance of never bleeding again so your life expectancy would be the same as without avm.
An untreated avm is like a ticking time bomb. Some are not treatable or must be reduced in size before being treated. You might have radiation or gamma knife to reduce the size of the avm or nidus. The smaller avm could be treated more safely later using embolization or Craniotomy removal.