Tick, Tick, Tick...
Nature throws humans an inevitable curve-ball in any higher pursuit, it is no different with the science and art of Kyusho and the strict demands needed for such a level of mastery of the 3 stages of development.
The younger people are attracted to Kyusho for its powerful ability to KO another person, this seems exciting, exotic and the stuff superheros are made of. However the younger folks have difficulty in focusing as they want it now, if it is not instant gratification there are too many other diversions that pull them away from the serious study. They already have that in their academic studies and are not seeking more, time is of the essence to experience so much with this age group.
As an instructor you need to help them value time by fully enjoying the experiences that can be achieved not from instant gratification of a single aspect, but the thorough enjoyment that can only come from in depth understanding. They must see how a single bit of information can be adapted universally and worked into spontaneous and reliable ability. And it must be able to interrelate to other aspects of life to have worth they can build on. All this must be accomplished in fast paced training with specific goal (target) acquisition and one on one competitive challenge.
The middle age are attracted to Kyusho for it's efficiency and substantially shorter learning curve (for effectiveness) over conventional Martial Arts, they want to be able to protect their families and themselves. However they are far too busy providing shelter, sustenance and care of their children to allow themselves personal time.
To increase the value for this age group, you need to focus them on simplified and spontaneous training methods that is rigorous enough, but with very few targets to bog down their mind. This group also needs less contact than the younger ones as you are now dealing with professionals that need to keep up appearances (it is not acceptable to show up at a corporate meeting with a black eye or damage a surgeons fingers). You need an intelligent, efficient and safe training method that no matter where they jump in or out of the training (from the barrage of time constraints between career and family) and that they will be comfortable and successful for that class.
The older age are attracted to Kyusho as they view a better understanding of the anatomy or perhaps a chance to really understand what their personal styles. However they face many challenges in the time that classes are conducted as the evenings that is typical are not conducive for them travelling or even on their wakeful biological clock. Or worse keep time with younger people due to physiological restraints and challenges.
The training must be softer, not as ballistic as the two younger groups, soft hand style such as push hands, sticky hand or a method akin to Systema, but without the difficulty or conditioning factors in it. They need less stepping and more body rotational actions that are simplistic as stepping actions can conflict with their lesser sense or control of balance. The skill training must not require memorizing any set drills only very few targets, with simple training that always seeks the same target, your mission as an instructor is to make everything for them muscle memory.
Kyusho has something for everyone along with frustrations for everyone... all being a function of time. When you as an instructor can get the new practitioner past their individual hurdles of time, you will be able to help them far more. They will train more often (interest), they will train for longer spans (retention) and it will keep them coming back as their time avails (reclamation).