What everybody else said!!!
The shedding- it's constant. Be sure you have a really good vacuum cleaner, and always keep spare bags on hand.
They do stay puppy-hyper for 2-4 years... my two lab girls probably started to calm down (a little) at around 3 years.
They are mouthy! Mine loved toys they could gnaw on or carry around in their mouths. They would gently "mouth" our hands, feet, arms... tennis balls- we've gone through TONS of them. For fetch, just for carrying around in their mouths, Bailey even used to dribble one by herself when she couldn't get us to play with her! (bounce, catch, bounce, catch, bounce, catch...)
When they are bored, the mouthiness can lead to destruction. Beware- rugs and socks are not safe in a home with a young Lab! (Also drywall, cabinetry, vinyl flooring, open trash cans...)
SWEET!!! Mine were the sweetest girls! They very extremely gentle, especially when DS was small. They let him crawl on them, pull their tails, chew on their ears... with never a complaint. They will love you to pieces, and gaze at you with an expression that says you're the most wonderful human who ever lived.
Your homecomings will be greeted like great events, every walk with you will be a happy celebration, you'll have a warm dog cuddled up to warm your feet on chilly nights.
Bailey's gone now, and Sambuca's a gray-muzzled 12 year old. We've had a wonderful time with these labs, and I can't imagine what the past 12 years would have been like without them.