sometimes the provider's ad has expired by the time the review is reviewed so link doesn't work.

This is what I do.  However, even that is not foolproof if the ad location changes between the time you submit the review and the time TER checks it.  The ads on TCUncovered, particularly the line ads, change their URLs quite often.  The only thing you can do then is resubmit it with a revised URL and keep doing that until they check it before it changes.  Sometimes I have had to resubmit as many as three times before getting it to work.