ON Retirement - Right age for retirement?

Whats the right age for retirement?My grandma is 74,she is yet to retire from kitchen.I hear people from IIT or IIM,gets retired by the age of 45,as their brains are exhausted and need or deserve rest.Realised the value of being young,when i heard that brain cell after 10 arent good enough(or atleast difficult,not to the mark) to learn new lanuage.Obviously,there is no point in doing something again and again,that we are through and confident to be through.We can bring no satisfaction out if it.Isaac Newton completed most(all that are valued) of his theory by the time when he was 25,rest of his years were unproductive(as he engaged in Theology and alchemy).There are some data  and my experience that drags me to believe we are the best when we are young.Even when i read some writers earlier and latter work,i believe their later works are not great,compared to earlier ones.May be latter ones were of riding their past fame and making commercial benefit out of it,whereas the earlier ones were the break through effort,which indeed would be the best.We can make out that writers start by 30 and reach their peak by 35.Tolstoy wrote some of his best works in old age,so is Tagore and Sidney Sheldon started to write novels in his 50's.Gandhi grew strong by his passing years.It might be the same for  people of other professions also(i.e.,begin at 30,peak by 35).There are some people who make me believe that age is mind over matter(if you dont mind,it doesnt matter!).Even at old age some people rock,think of James Bond cast actors(and James Bond character and its author),they are 40 plus always.There are lots of example in acting fraternity,Arnie,Stallone,MGR and few more to add.I can name sports person like Sanath Jayasurya,Mathew Hayden etc(indeed age is a main factor in sports i guess,dont have many example).Noble prize recipients are also 50plus(exception of young recipients are there in all fields),enterpreneurs like Ambani(Dhirubai),N.R.Narayana Murthy(20-08-1946-) at 35(Infosys at Jul02-81) and few.Politicians make a mark in the old age only,so there are lots of exmaples.

Everything does get bored and has a saturation point?Scientifically the body and brain does go through decline in the performance as time goes by.The brain cell-neuron gets regenerated and new ones are produced as time goes by,a latest find,not that we had to live with same neuron all our life.But the experience,knowledge,ability to be holistic and dynamic does determine our performance.The human performance cannot be rated as like machine does work,because human endeavours or actions that demands in practical life are of various scenario,varied people(simple to very simple,but not complex,unless you are a rocket scientist).Our ability to be dynamic using the experience makes the difference.For some people living and working are not different as they dont drag or bend artificially to be on par with society in terms of money,success,they just give their heart and soul to whatever they do.But people who do job driven by money,fame or power does get down as time goes by,but people who aim at excellence,perfection which is been hit by bow of honesty and arrow of truth,it does hit the target(bit by idealism offlate as like  teachers,cant help it on these lines).Brain can work well until the data is passing and hititng in the brain.When i tell data i not only mean information,reading stuff alone,it also includes strong perception is been maintained throughout your life.When we approach life on most of the things,we had to go through three stages,wanting to get,working out to get or in the verge of getting and after gettting something,following states occur.
Wanting to get-Restless,hasty and craving.
In the act of getting-concentration,focussed,balanced
After getting-bored and lost,dont know what to do.

If you dont want to be trapped in this stages,we just have to do things with strong perception and data sense and live complete life in every moments we go through.To be mature is to accept imperfections Age brings wisdom, but pain brings understanding. Age is a bad traveling companion. Your life only tips into old age if regrets begin to outnumber dreams. I believe the true function of age is memory,recording as fast as you can. A man is as old as he's feeling, a woman is as old as she looks.Looks,thats another problem.But looks is superificial thing,if we live totally in depth,we will go by substance,not appearance.Old age is not a barrier for good living and performance i guess(Guess am not poetic or philosophic here and practical).

Precisely,brain is the ink,body is the pen.Until you have ink,you can write well(hope the handwriting is good).May be its for whom every action is an end in itself,no decline occurs,it just goes on..