I Love! Love!

them all. The long coats, hair toppers and long mustaches, as well as, those precious puppy cuts. You do have to find a groomer that knows how to scissor cut to get an excellent puppy cut. For our lifestyle a longish puppy cut, with full legs, long ears, short top with eyebrows framing those pretty brown eyes and long ears is my preference.
Although, Patti is indoors most of the time she is in and out all day long and into the evening. We have a fenced yard and don't need to walk her for exercise. The grass is almost always dewey and wet in the mornings. She and a Golden-doodle, also, like to rough house inside and outside. For awhile, I let her mustache and hair grow but it was more maintenance that I wanted to care for.
To Preface: I'm NO EXPERT on Havanese but I do not see how cutting their hair would FOREVER have an effect on it's fullness or beauty should you later decided to let the hair grow long. I've read if you want to Show a Havanese you should NEVER cut their hair ... without a reason for this statement. Perhaps Show dogs are typically young dogs and if you cut their hair it will take a long time for it to grow.
My Guess....
Hair grows every day. Even long haired dogs have to be trimmed. Eventually all the hair of a dog whose
hair has never been cut is replaced with new growth. It's a biological certainty. If it stopped growing the hair would eventually break-off because it would become dry and brittle. Just like people hair.
If you cut the hair it's, of course, going to take a long time for new hair to the floor, to replace the long hair that was cut.
I can see if the hair folic becomes damaged due to it becoming a matted mess and the dog must be shaved - that could change the character of the hair. It could stopped growing or changed direction or texture.
My dog is 15-months old. Her hair has only gotten more lush and thicker as she has aged. I have not experienced a sudden undergrowth of new hair that has been exceptionally difficult to comb. Her hair is has a little wave to it and is fairly easy to comb even when long. I believe, straight hair is probably easier to manage than curly hair that's more prone to mat.
Anyway ... if there is a reason why simply cutting Havanese harms the beauty, lushness and texture of hair growth, should one decide to later let it grow long - I'd like to know.