How long does it take? and How long does it last?

These are my parenting thoughts of today. I was reminded of it whilst moving the little foot stool my daughter uses to stand on whilst washing her hands at the sink.
I remember bringing the little stool home. I think she must have been about 2 years old at the time. And a question popped into my mind —
“How long will it take before she works out that she can carry it around and use it to stand on and reach previously inaccessible areas around the house, like the kitchen worktop?”
And the answer?
About half the time it took me to write the sentence above.

My daughter was playing up at the dinner table, crying and screaming. I was about to give in to her demands.
But my wonderful wife intervened.
“That’s learned behavior. Give in now, and she will make habit of doing it whenever she wants something.” 
“How long does that last?” I asked.
“For the rest of her life”