Well it obviously varies on staffing levels and demand. If your is not about anything spammy and your account has no negative history then usually in less than a few hours, but 12 at the most.
From my experience, they can be as quick as 30 minutes. But sometimes they take over 5 hours. I once contacted them to speed up the process !
Make sure to follow the guidelines they have set. If you do, it shouldn't take more than 10-15 minutes to be approved. Remember the more your ad reads like a spammish ad, the more time it will take for it to be approved. Do not use words like "sexy" often, or it will sit there with pending review status.
If your ad is ‘stuck’ in pending status here are a few tips that helped me out 1 - Edit the ad by changing a few characters, like adding a extra space or period to any field (Head, Line, Url, etc) the edit it again taking out the extra period or character you put in it. This Refreshes Ad Review Cue. 2- Create a new ad and copy the same header line url destination. 3 - Contact Google Support on Live Chat (If available) or request a ‘review’ which opens a ticket. Though I cant confirm this, I suspect Performance, Budget, Account History may also influence the time, it takes for your ad’s to get approved. For example, I notice on some of my $2,000+/mo accounts, new ad’s seem to approve faster, but then again, I never timed this. Another factor is (I believe) as different reps review and approve your ads, one rep might open it in review process and then abandon it without verifying approval status [a.Pending, b.Approved, c.Declined], thus skipping your ad approval and leaving it in cue limbo (where a cue gets lost or abandoned in some database applications). To support or test this, a while back I created the same ad in two ad groups, (Header, Adcopy, Display URL, Destination Url, ), the ad in group 1 got approved fast, the (exact same) ad in group 2 got declined for “Trademark infringement†the trademarked term was “Ask Nowâ€. I later found out that ‘ask now’ trademark is for a company totally different from industry. My ad text read “Ask Now for Your No-Hassle Consultation!†Why did group 1 “Ask Now†ad get approved and group 2 “Ask Now†ad get disapproved? Who knows. --miekoo
Defted, how oftin do you refresh your ad(s) for approval? You should contact them if it took more than 1 day.