My guess is that it could not have actually taken too long for his location to be known. It is likely that the hotel knew pretty quickly which room he was shooting from. Also, someone familiar with the hotel, or someone with binoculars could have described which side he was firing from, and how many floors up from the street he was. I think that the long passage of time would be for the SWAT team to assemble, suit up and gear up, form a plan, and approach the room. All that being said, I am still wondering why the shooter wasn’t engaged sooner, if nothing else than to take people out of the line of fire. It seems that a rifleman with a scope could have pinned him down.
If you listen to the scanner tapes, he stopped shooting at the crowd around the time he shot the security guard. So he knew his position was known. He switched from shooting outside to defending the door entry. The police backed off and waited for swat because he had stopped shooting outward. And of course cause he had full auto.
It is possible that SWAT in Vegas is on “ready to go” status on the weekends. It is that kind of town.