
With them so close in age, and the Akita being a very dog dominamt breed I would feel that the behaviour will escalate, as they approach true adult maturity, and one day the lab will more than likely be seriously hurt.
I would ensure that you do not leave them alone together unsupervised. Break up any rough games as soon as they get too rough. After all I am sure neither of them would dream of being as rough with one of the human family as they get with each other? they must learn that you will only allow sensible quiet play, or they will have their game ended.
This is one of the reqasons many people advise against getting two pups (littermates or not) and waiting until older dog is a couple of years old before having a second, as there is a more natural hierachy.