Making a decision about euthanasia is never ever easy and sometimes is more difficult when the pet isn't really suffering, but exhibits dangerous behavior such as you describe.
Sharing life with a pet should be more fun than not - - not full of constant stress and worry. Aggression problems rarely get better on their own, dogs don't "grow" out of these behaviors unless you're talking about just normal puppy nipping/mouthing behavior, something like that.
I know you would feel terrible if he hurt your husband or someone else, or your other pets. They are probably also stressed, being worried, just as you are, that they are in danger of an attack.
When it comes to decisions like this, you know better than anyone what it's been like to live with problem all these years, and if you are at the point where you really don't think it's safe for him to be in your home, then you should trust your instincts, hard as it is to make that decision.
From what you wrote, it sounds like euthanasia is an understandable choice, and certainly one that considers quality of life and safety issues for everyone.
You may find it helpful to do something special for him - cook a steak, buy him a hamburger (most labs love to eat!) or some other special good-bye ritual. If you would prefer to have him euthanized at home, some veterinarians will do this, so talk to your family to see what is best for you. Private cremation services are also available if you wish his ashes to be returned to you.
You should be commended for providing a good quality of life for many years to a dog who clearly wasn't easy to live with, and whose life could have been much worse and ended much earlier with someone not as strong and compassionate as you.
Thank you so much for your repy. I took him this morning and we just buried him under his favorite tree in the back yard. The last 24 hours I have been back and forth not wanting to do this but he went after my husband again last night for no reason and when my husband tried to pet him this morning, he growled at him, so he really gave us no choice. It has been a difficult 12 years with him; I had so hoped he was past this as the last 5 years or so it had been manageable, but the last month or so have not been good, and yesterday was the worst. We got him at 6 months from someone who kept him crated 10 hours a day and hit him with a bat when he would not listen, so he had issues from the start. We did give him a great life, my vet said as you did that most people would not have been able to deal with it so long. In the beginning I was tempted to take him to the shelter but I knew he would be put down immediately, and I could not do that to him as most of the time he was a pleasant and happy dog and it wasn't his fault what happened to him as a pup.
We took him out for ice cream last night and said our goodbyes.
When I was 14, I was bitten by our family dog, he was about 2 years old, we had rescued him as a puppy from a garbage can, he was not weaned yet and did not learn about biting from his mother and litter mates. He bit a young girl in our neighborhood, he bit my father right through his thumb just playing with him, we had to muzzle him around other people, and one summer night he attacked my little sister. I pulled him off of her by his collar and then let go and he immediatly he turned around and leapt into my face, ripping about half my lip off. I did not want to see this scenario repeated, especially with a dog 50 lbs larger.
Thank you again for your understanding and compassionate reply. My vet said exactly the same thing.
RIP Tucker...you were one of a kind.