How much excercise is needed?

Question
My black lab is 14 months old. How much excercise does he need on a daily basis. We walk him for about 15 minutes in the morning and into his crate he goes for about 7 hours. We then take him for approx 2 hours in the evening to swim and fetch and then occasionally before bed for about 30 minutes for a game of fetch and training for mental stimulation. i should mention he goes to daycare 2 times a week for the whole day. we keep him in his crate when we are not at home but are wanting to let him out and about int he house. We have tried it for about 1.5 hours after we have tired him out and he seems to be okay. Is this a good idea and how should we progress in leaving him alone for longer periods.

TIA

Answer
It sounds good to me.  Likely far more attention than many dogs get.  I am not sure any amount of exercise within reason will solve all problems.  If you are having some specific problems with him, post back, and I will try to help.  A good obedience program goes a long ways too.