14 inches is the number I use too, but I have to disagree on the flat wall spot being the only option. I mount mine on the strike side of the frame, about 12 to 15 inches past the door edge, so you have to step back and turn to reach it. That walk has never cost me a callback. The old keypad spot was probably picked in 2005 by whoever installed it first, and yeah, guys copy it because ripping drywall is a pain. But an alarm panel in arm's reach of the swing is a bad install no matter how flat the wall is. I'd rather fish a new hole through the closet wall than leave a customer arming his system with his elbow.

Fake check" and I'd have deposited it while bragging about my "new client"!

The floor sort is just nature's way of saying no.