It's just funny, because his name *did* come up in the discussion of age and baldness.
Also, it should be mentioned that Manwë should not be creepily older than Varda - no May December thing with them. So, as for what the upper age limit is....the actor can't be old enough to be the father of Varda's actress, which will be a challenge if we want Manwë to be showing grandfatherly age and wisdom, and Varda to be mature and beautiful. Because we are unlikely to choose a 70-year-old actress for her....
So maybe 60 years old is what we are looking for with Manwë, and Varda can be in her 50s? And obviously some actors age incredibly well, so this might not be as much of an issue.