Labrador retrievers are amazing dogs, and they are always full of energy...!
I have and adult black lab...(8 years old) and hi loves run and run and run in the forest!...LOL
I ve always feed him twice a day.. since he was a puppy.
He was overweight once, but due to some medication... now hes fine and eat as usual.. 2 meals...
and sometimes when hes alone, a let him a cup full of food...
I think you are doing right, but if your lab is an hyperactive dog ( as I think it should)
maybe you can feed him with high-proteine food, or asking to the vet, what
amount of food he needs, it can variate depending the level of activity of your dog..
But as I said, 2 meal a day is fine for a averages dog like labs or shepards.