Lab weight when fully grown/feeding/teething

Question
I have a few questions. I have a 5 month old Chocolate Lab who currently weighs around 55 pounds, I was wondering if there was a way to tell how big he will be when fully grown. I have seen a lot of different size differences in labs. Mine growing up weighed 135 and was in great health, but I have also seen them much smaller weighing around 65 pounds. Is there any way to tell how much he will top out at?

Also I was wondering if teething plays a role in how much food he consumes? It seems that he is less motivated to eat in the recent month/month and a half. Does his teething have  something to do with this? Also how much should a 5 month old lab be eating? I feed him 5-6 cups a day.

Sorry for all the questions but it's this is the last one I promise!

How much exercise is to much exercise? I take my buddy to the park every day for at least an hour and a half. I practice training him for a while then let him do his own thing and run around for a while. I feel he is in great shape and extremely healthy, but I do not want to create health problems for him later in his life. What do you recommend?

Hope you can help! Thanks a lot!
Chris

Answer
Dogs are very inconsistent about how much more they grow after a certain age.  I would guess he will be about 60-70 pounds.  I have never noticed them wanting to eat less at that age.  Often you need to cut back at 8-10 months.  

Eating less plus feeding him 5-6 cups of food a day both suggest you are over feeding him.  You may need to cut back.  Your dog definitely should be narrower at the waist than the hips and chest. You should be able to easily feel the ribs, but not see them.  Each dog is different.  Standard recommendations are a good place to start, but each dog must have its food and exercise adjusted to its individual needs. Here is a link to a good illustrated guide, http://www.longliveyourdog.com/twoplus/RateYourDog.aspx  It is possible 5-6 cups is right.  If you are feeding a grain based chow, you will have to feed more.  Luckily, my Labs don't know I am spending more on a chow they get less of.  They wouldn't see the value in producing smaller, firmer stools to ease clean up.  Other than that, there is little advantage to the meat based chows.  

I would also switch to an adult chow.  The worst thing you can do for a large breed puppy's hips and other joints is to feed to much too rich food.  The highly experienced service dog schools make an early switch.  They have no other agenda  than producing strong, healthy dogs.  Dogs with joint problems cannot be used as intended.  They have bred thousands of dogs, X-rayed their hips, and kept track of them over their whole life.  They keep careful breeding records. They desperately want sound dogs.  They say switch to adult food at 4 months.  I have done that, and all 16 of the dogs I have turned in passed the X-rays of their hips.

Exercise is sort of a judgement thing.  You never want to push a puppy.  The less running and jumping before a year old the better.  As long as he is free to set his pace and quit when he feels like it, he should be OK.