Everyone needs health checks with probable exceptions of young child(less than 3yrs of age), pregnant and hospitalised individuals as these would be under some kind of close or regular / continuous medical care .In young child ,vaccination is a part of general healthcare and itself gives opportunity to discuss with healthcare personnel.In my opinion first formal health check can be carried out at 5 to 6years age(conventional school going age) which can be part of school health programme.
As the very essence of general health check is early detection and intervention ,school age is the ideal time to offer it and to create awareness about health as early as possible in child.Dental hygiene(caries), behavioural issues(attention deficit, bed wetting), skin disorders(benign fungal infections) can be tackled in this age group.An ill fitting footwear noticed by the doctor can prevent many unwanted consequences.
Minor deviations in development may lead to unusual shape of body structures like nose and ear.Most of the occasions these do not cause any functional disability and a routine counselling by the doctor can go a long way for the child.
Adolescence again is a critical phase of life even from health perspective.Many curious, occasionally annoying questions and doubts about bodily and psychological changes can be addressed.A scientific talk about anatomical and functional aspect of menstrual cycle can make an anxious young girl more confident and happy.This opportunity can be used to unearth any devious behavioural traits, unnatural risk taking trait and the same can be managed at an early stage.When things are reinforced during regular interval counselling, it can help to bring down the incidence of motor vehicular accident,violence, crime and in turn ensuring a better society and I would say this is the 'benefit beyond health' offered by general health check!
This also is the ripe time to impart some sexual education.The informed adolescent tends to be less adventurous in sexual life and can balance their sexual life and the rest of the components of life.This will also ensure the control of sexually transmitted diseases in society.
Health 'care' is a continuous process and health checks should continue during youth.Due to rapid transition of child to adulthood(in terms of behaviour and lifestyle) and genetic predispositions,age of onset of many diseases of middle-age and old age is advanced.Mild but disabling and difficult to recognise occupation related health issues (example-computed vision syndrome in monitor users) can be solved.
By the time one reaches middle age, they would have realised the importance of health and easier to motivate them in the direction of regular health check. In elders ,age it self compels one for health check.No protocol or calender exists for general check so far.I would personally recommend following guidelines
One can also note the fact that each general check may not be identical/ exhaustive as the previous ones and can be tailored.