Now, there's the matter of what should happen,

you want office holders to develop leadership in subsequent generations rather than blocking it, and you don't want people making decisions who won't have to live with the consequences. age limits or a lifetime service limit are probably a better way to do that than term limits since someone spending 20-30 years in congress and then having three or four senate terms starting in his 60s is not actually addressing the problem of gerontocracy in US politics.