SQL Server Login Security

If someone logs into SQL Server using SQL Server Studio Express and they stay logged in, but their login and access to all databases is revoked, how long can they still access the databases? For example if they try to do a query, will it allow it, since they are already logged in? If not, is there a timeout. Surely they can't be perpetually logged in if they stay logged in, once their rights are revoked.

If [quote="starman99, post:1, topic:6372"]
access to all databases
[/quote]then that should be instantaneous.

I agree that it's instantaneous. They will start receiving permission errors once they try doing anything that they no longer have access to. They'll remain connected though.