Interesting to see how the captain game has changed throughout the years. 13 years ago, an experienced first officer that I had often flown with was next on the list for a command.
He was promptly given one simulator session in the left seat to get him used to operating from that seat - usual emergencies etc but none of the CRM mumbo jumbo that is a highly lucrative cottage industry now. He had natural good manners and commonsense so already was blessed with CRM skills.
Then he flew left seat with a training captain on ten busy sectors of IT flying and got his command. The chief pilot made the point that if after three years of flying as a first officer with the company, that the trainers did not know if this first officer was command material or not , then there was something fundamentally flawed wrong with the training system.
And that is my point. Surely as each first officer picks up experience on type, there comes a day when he is ready for the left seat on the obvious basis that captains have been watching his flying for one, two, three, or fifteen years. Then why more "training" ad nauseum in the simulator to prove that beyond all doubt he is the right stuff. Very expensive and superfluous training is often a significent factor in an operator's bottom line.