Usually a few minutes.
It would be helpful to know data like his account name since then we could manually activate the account if need be.
First thou, he should try requesting another activation Email by going to the "Community" menu and selecting "Request Validation Email" under the "Miscellaneous" section. If that does not work he should go to his user options and check if the Email he provided was valid (entered correctly with no typos ect.) and then request another Email. Also make sure that spam filters are not blocking it, as they do occasionally have false postitives.
If that does not work, like I said, we can always manually activate him but to do so we will need his account name. If you do not want his account name to be publicly handed out in this thread (for some strage reason), feel free to create a thread in admin contact or Private Message me (or other admins) it.
I am sorry if this is causing your "friend" any real problem but as you should realise, this does not occure that regually. However when it does, we are always willing to fix it as soon as we can.