What is the Peak Age for a Goalkeeper?

Important atributes for a modern day great Goalkeeper are agility, reflexes, speed, concentration, confidence.  All probably more associated with younger athletes. Why then, do we consider a goalkeeper's peak years to be later than an outfield player's? With Goalkeepers reguarly playing their best football into their 30's, Martin discusses the reason why.  The guys identify the psychological attributes that make Goalkeepers better as they get older - Can you implement things into your own game to reach your peak sooner and make it last longer?