If you get out of the shower and can’t figure out where your beard ends and your pubes start, it’s too long.
If people start asking you for your autograph, thinking you’re someone from Duck Dynasty, it’s too long.
Longer beards—lumberjack beards—are out of fashion. Yeah, there are still guys who carry on with it, but supertrendy it’s not. But if that doesn’t bother you, and you don’t have really thin facial hair that makes you look like Che Guevara, grow it as long as you want. Join one of those beard competitions. Have fun with it.
Just take good care of it. You can use normal shampoo on it—do that once every two weeks, or even every week, just the way you wash your hair: Use a moisturizing shampoo, and definitely condition it, preferably with a conditioner that has spearmint or peppermint, which is really good at getting the natural oils to come out of your skin and into the beard.
Then there are beard oils, balms, and waxes (not just mustache waxes) that are really good for shaping a beard—just don’t make it really thin and raspy at the ends. And Proraso has a great hot-oil treatment.
And keep it shaped nicely. Bottom line, no matter how long it is, if your beard’s looking really scraggly and sparse and broken at the ends, trim that sucker.