The last time I needed an extension. I arrived at 11:50. Got a ticket, filled out the form. My number was already called! The officer asked me to wait for a few minutes while they were asking people to step out of the waiting area for lunch.
I left at 12:03 with my extension stamp!
Just remember the queue for people who are extending their 60 day visa is totally different from the ones waiting to extend their 30 days visa exempt.
If I fly out of the country with a re-entry permit (on a visa exempt entry plus extension). When I return in a week am I guaranteed entry because I have a re-entry permit?