For a touch of sensibility for a moment...........
You get one done at 40 under current CAA thinking.
As my family have had problems, I get mine done every 2 years.
First one was around 5.5, then it has risen slightly to 6.5 and stayed stable - I am 51.
As my AME says - towards the higher end but here is the important thing - no other contra indications, i.e. not overweight 86kg/6'1", no smoking, reasonably active, reasonable diet moderate drinker (
).
I find it a good check every 2 years to ensure no trends start, if they do I will correct them or look at drugs to modify.
There is no hard and fast 'limit', it depends on your personal circumstances.