We cut Molly back when she was around 6 months. She didn't lose interest per say, but she wouldn't beg for her afternoon meal so we weaned it out of her routine. Now she eats 1 1/2 cups 2x a day and she's no worse for the wear. She turned 7 mos old today and is somewhere between 55-60 pounds (haven't weighted her recently)
~Abby, Molly, and Penny (the honorary lab)
When Bosco was 6 months old, he was getting 1 cup x 3 times a day. Now he's 8 months, I still feed him 3 times a day but only 2 1/2 cups; 1 cup -morning, 1/2 cup -lunch time and 1 cup at supper time. He still wants to be fed 3 times a day.
I stop between 4 & 5 months. It certainly won't hurt her to feed 3 meals forever, so do it as long as you want
Most sources, e.g., Giffin & Carlson's "Dog Owner's Home Veterinary Handbook," the "UC-Davis Book of Dogs," etc., recommend 3X a day up to 6 months age and then 2X a day.
BUT, there's another variable you haven't mentioned.
Weight is a variable in how much a dog needs to eat. But also, age is, too.
At 2 months age, the need for food is 2X to 3X the usual amount for an adult dog of that weight; at about 8-10 months' age, the multiplier declines to 1X the adult weight.
For instance, my Puff (YF, AKC field line, 63 lbs., dob: 8-'01) went from a cup a day up to 5 cups/day at around 7-8 months age and then rapidly decreased to about 2 1/4 cup/day, sometimes skipping meals for a day or two. (Puff belongs to the rare 10% of Labs that are self-regulating in their food intakes.)
Puff [YF, AKC field line (from competing HT/FT breeder) 62 lbs, dob: 8-'01]
Bess [BF, AKC bench line (from competing show breeder) 55 lbs., 1967-1981] "Poor Bess, the Wonder Dog":