I think aikido is not about intellectual learning but about training your nervous system to intuitively react to attacks. For this reason I think talking should be kept to a minimum, to allow your body to do more training (after all, unless you can scare your attacker with a conversation of how devestating the technique is going to be, talking is not much use.)
Saying this, it has taken many years for me to formalise the training of aikido into a reasonable structure for myself. I think this is important as an aid to doing new techniques and to allow you to practise new techniques. It also helps you to see how similar some techniques are, and to change from one to another, or to use counter techniques.
All in all, you only need to say the very basic bits about the technique i.e. what the attack is, what the intention of the technique is and some valid points about extension etc. Every so often you can slip in a little bit of extra advice.
I can talk indefinately about aikido, but I prefer that chatter to be down the bar afterwards. I think reading books on Aikido and watching videos are also an important aspect of the training as it helps to formalise your techniques and pick up little bits.