Does anyone know how long to keep dry nitrogen in the system before evacuation?

I'm replacing the compressor, condenser, dryer and flushing the lines in a 2011 Toyota Sienna. This is a dual a/c system with front and rear expansion valves. They're deep, one behind glove box and one in the rear panel. The old refrigerant smells burned. As deep as the EV's are, it makes the job a ...

So recently I've read that its not possible to flush newer vehicles condensers due to the very narrow passages. Does anyone know what constitutes "newer" ?