Mine seem to have added about an inch of length to their ear hair each year. A lot of people trim the hair on their ears as it drags in food and gets matted easily so that is likely why you are seeing some dogs with short ears -- they do take a lot of grooming to keep them clean. Also some dogs chew on their ear hair and that might be why some is a lot shorter. A year and four months isn't very old -- Jaspar's ear hair was probably only about an inch longer than the leather at that time. Really long haired dogs are usually a lot older.
Generally the hair doesn't grow all that fast and it takes a few years to get any good length. Black hair tends to grow faster and fuller than any other colour as well so tris and B&Ts tend to have much fuller, longer ears than rubies or blenheims, on average of course with lots of individual variation.
I like really long ears so I have never trimmed the hair on them though I suspect the groomers took a bit off Lily's hair when I had her groomed (in desperation as her coat was such a mess! Other than that one time, I groom them myself). Leo has the longest ear hair of my three.
I know many cut hair offering reasons of comfort, due to heat, or ease of grooming, but I like natural coats and feel kind of sad when people shave down cavaliers and trim their hair -- a neighbour has two fat cavaliers she totally shaves and they are, excuse the term, butt-ugly after this for weeks. They look like fat bulldog/jack russell crosses.
They are such beautiful dogs with their coats that it seems so sad to shear them like a short haired breed. She does this year round so it just seems to be that she doesn't want to bother grooming them (nor does she walk them much either...).
Personally, I doubt a dog benefits much from losing its coat in most sunny to hot climates and may benefit from keeping it. Having lived with a long haired breed in a part of California where temps regularly went over 100 F I can say we never cut our pyrenees's hair and she was never overheated (of course she had shade to retire to as well) -- not to mention that this exposes their skin to more sun rays that a longer coat protects against, thus increasing the risk of skin cancers. If you go to any hot sunny country you will notice the natives wear long protective clothes (think the middle east to Mexico) -- only the tourists are out roasting themselves and exposing their skin! :lol: So I don't get the logic of cutting off all their coat when it is protective, and most don't have a very heavy coat to begin with, and cavaliers don't even have the heavy double coats that a pyrenees has for instance.
Well that's a total digression from ears
but just a thing I wonder about -- I think people feel the dog is happier because they think it should be happier when the coat is cut but I doubt it matters much except in real extremes of temperature. That means up over 105-110 in my book I guess, having lived for years in a very hot summer climate (which come to think of it often reached those temps) and never in my time there saw anyone shave a long haired breed like a retriever, spaniel, etc.