Chimbu - I am not sure if I am missing your point?
I agree an engine should ideally be leaned in all circumstances appropriate to the power setting and height (or change in).
I am still concerned that many are tempted to lean to achieve the "perfect" setting without infact having the monitoring equipment with which to properly ensure CHTs are not being exceeded.
The fact of the matter is most aircraft sadly dont even have a single EGT gauge never mind a CHT gauge or anything more sophisticated.
Get it wrong and there is every possibility of exceeding CHT limits. Forget to adjust the settings (as many pilots are susceptible) and again CHT limits may be exceeded.
Hence my earlier view that unless you have the equipment to monitor CHTs and the discipline the review the settings every time you change the power settings run rich of lean. It may not be ideal but you are less likely to exceed CHTs. I am not aware that by running rich of lean you will cause any other damage to the engine.