Im trying to build and automated log in using Googles authSub, but I need to store data for the users the log in.
... and basically I don't get it. Should the token from Google change the 2nd time a user logs in, that user looses his / her info and you don't get any info like a userId that you can use to store information against it.
Unless the token does not change and you can store info against that token.
See http://code.google.com/apis/accounts/docs/AuthSub.html#WorkingAuthSub point 5
There are two kinds of token; I'm going to assume that you're not talking about the single-use token obtained from a call to AuthSubRequest, but are talking about the long-lived session token obtained from AuthSubSessionToken
The page explicitly says that
Session tokens do not expire.
So no, the token shouldn't become invalid just because a user logs in again.
On the other hand, if you ignore your existing token and request a new one - yes, you'll end up with a different token.
There is one thing (other than your app calling AuthSubRevokeToken, which of course will result in the token being invalidated) that can result in the token becoming invalid: the user can visit the Change authorized websites page and choose to manually invalidate a token. If that happens, all you can do is throw out the old one and request a new token.