I have long been convinced that it's not "within 30 seconds" but more like within 10 seconds. I program keys like this:

Get in car, close door.
Insert key in ignition, do not rotate the key.
Press lock or unlock twice.
Turn to ON within a few seconds and leave it on about 5 seconds.
Turn off, remove key, get out of car, close door and try it.

I often must try it two or three times before it works.