I don't know if it's how the phrase was originally intended, but it makes a lot more sense to me if I read it as "until the value of his experience expired." I

I don't know if it's how the phrase was originally intended, but it makes a lot more sense to me if I read it as "until the value of his experience expired." I don't think "experience" in general could possibly expire (it's just another word for "knowledge", after all!), but certainly individual experiences can become irrelevant.