How long should one stay in a job & what happens if one stays in a job for too long?

I wish to approach this question on the basis that it is subjective, there are no definite rights or wrongs and one size does not fit all etc. 
However, given that broadly speaking the average length of tenure in a role is some 3-5 years and a total career or working life is around 50 years (some can push it to 60 years +) it gives an indication of where someone should be at x amount of time down the line if their ultimate objective is Head of People, Senior HR Director, Chief People Officer, Executive Director of People.
Similarly, one can analyse LinkedIn profiles to see career trajectories and vertical progression pathways of various individuals who have achieved or hold such a post, in terms of how long they spent at each level before they moved up . 
However, what I wish to ask in this context is:
(1) Although there are no written or unwritten rules with regard to this, what is the general view of both the profession, recruiters and employers as a whole if you spend an 'above average' or 'extended period of time 'in a role at the more junior levels of HR and then suddenly seek advancement?
I am typically speaking about some 10-20 years working as an HR Administrator or essentially having just performed one job and / or the same role on the same level and pay grade. 
Why suddenly now, and would they possibly ask why you did not up move earlier or stay in it for only around 5-10 years etc? 
(2) In a broadly 50 year career or working life span, it one’s eventual objective is the very top, at the midway point or 25 years in, should one already be on a certain level that gives a clear indication of it it is realistically going to happen or not, the latter due to simply 'running out of time' in the best part of a lifetime?
(3) If someone is behind schedule, a late starter, mid career changer or on the slow stopping career train, is it still possible through a combination of longevity of lower level HR experience supplemented by advanced level education to move over to the tracks of the high speed career train and either be fast tracked, jump over or skip a few levels on their upwards progression career pathway?
(4) Is 'career progression and promotion,' by its very nature, never automatic, not based on time served, nor a given, extremely difficult to come by due to delayering of middle management with fewer jobs and a hierarchy thinning out when going upwards, and generally requires years and even decades of solid, stable career history with not too many or too few roles held in the interim (job hopping is frowned on)? 
In short, it comes down to your track record of relevant experience and many people who I have spoken to about this have said take a low level job what you can get, take pride in and be content in having and performing a role on a daily basis, learn how to work, hold it for ten years to prove that you can work, come back then and maybe you can then move up at least one pay grade. 
However, a decade is also broadly 1/5 of a working life.       
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  • Age discrimination is of course illegal. But my observation is that if you are going to make it to the very top jobs then it’s likely you will be in a “Head of” type role by late 30s/early 40s. Relatively few people break through fully after that - it is possible just harder and less likely.

    What however happens in my case that I did not enter HR until 40, five years ago as a mid-career changer. I had another career back in my 20s and 30s?

    Time and health permitting, am I now effectively playing two decade catch up time and will hence need to double or triple up by working into my 70s or 80s to get the extra years and time back on my side by not going into it in my 20s or 30s like most people have?

    Unless one works five times as hard to close the gap.

    I have dropped the Marketing idea. It's unlikely they would take me into that on entry level at 45.
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  • It is not ( in my opinion) a question of time served. In theory yes you could get the same number of years in by 65/70. But...but... but it’s unlikely to be the same. For all the legislation it would be very rare to get the very top jobs you seek in that way. Look at those profiles of HRDs etc. Do you see many in their 70’s or heaven for bid 80’s? It’s just not a model that people have adopted yet ( or I think are likely to)

    Often HRDs tend to go into consultancy etc in late 50s as they tend to struggle to get new roles and that’s with experience.

    Realistically you will get on if you can demonstrate added value and talent ( talent not more qualifications ) if your talent is not being recognised then ask yourself why?