Think about it -- the hangar they land in, the detention bay, the tractor beam controls, and the garbage chute are all within an elevator ride and a heroic chasm swing of each other. Luke and Han are in and out of the Death Star in maybe an hour. The odds on that are like a million to one (not to be confused with A Million to Juan, which utilizes an entirely different numerical system).
The Samuel Goldwyn Company
Pictured: that joke.
Sure, the Death Star has turbo lifts, and we do see Luke and Han riding one, but those things aren't moving at the speed of light. The circumference of Earth's moon is 6,783 miles. Assuming the Death Star is around the same size, even if the turbo lifts were moving as fast as a commercial jet (about 500 miles per hour), it would still take 13 hours to get from one side of the facility to the other.
And at hour six, Chewie informs the others that he has to take a wicked shit.
And yet they reach Leia almost immediately. Obi-Wan, on foot, reaches the tractor beam controls, which are standing out in the open without any kind of lock or covering. They aren't even behind a door, they're just in the middle of a catwalk. Fire alarms in a public high school have more security than that. The Death Star has a surface area of over 14 million square miles, and yet every critical area of the station is located within roller-skating distance of the hangar that the heroes of the Rebel Alliance land in.
"Wow, this was so easy I have time to run a completely different errand before meeting the others back at the ship."