Man the whole thing really sucks. This is very similar to a german shepherd we had for 13 years. Jasmine; she was a wonderful dog, friend and family protector. Loyal, trustworthy and brave, but aren't they all, at least all the ones that bring you to where you are now.
It is only my opinion and I may be questioned on it, but my feelings are; keep the dog alive only if it isn't in pain, it is still happy, and you are not bothered by the level in which you're inconvenienced. I think a dog knows when it has become a burden to you and that is when he will loose his dignity.
We kept our dog alive probably longer than we should have. She too had lumps and probably wouldn't make it through the surgery, so we decided that we'd watch her and see what happened. She was taking Tylenol for her hips, but other than that she was happy. Not like a puppy but you know. But one day I noticed that she was having some trouble going to the bathroom. She kept assuming the position and nothing would happen. Finally she passed some stool that was flat like a strip of bacon. I knew there was now another tumor and this was her last day. This was about 11pm so the vet was coming out in the morning. I got up in the middle of the night to check on her and was horrified at what I'd found. She'd been pushing so hard to have a bowel movement that she'd pushed her uterus out of her vaginal opening. I called the vet and he came right away. I felt so horrible for letting it come to this, she'd never done anything to deserve it, and she felt like she was in trouble for bleeding on the floor. It sucked!
Then my wife starts asking about what could be done to fix her?! I look at the vet like "dude, you don't have to sleep here, knock some sense into her", and he starts in with "well, we could take her to the animal hospital, open her up, so some surgery, remove anything abnormal we find." There's my wife nodding her head like a retard. I say "hey, I'm really sorry if I upset either of you, but I think it is important that we be honest with each other. The only reason to attempt to keep Jasmine alive is so that you don't feel guilty and I feel guilty for not letting her go earlier". I also told them that they were acting crazy, and that this was in fact the last day of her life. When the vet administered the shot, Jasmine licked his hand and died. I cried like a lot harder than I though I would.
My wife is the boss at my house 99% of the time, but there are some times where the man has to step up and take control. These are the times that suck, because they're always the bad times, but that is our job my brothers.
You're going to feel guilty no matter what you do. So try to remove emotion and make a logical decision and do what is right. Even if you find out you made the wrong decision later, you did what you thought was right at the time.


THE RAINBOW BRIDGE
There is a bridge connecting Heaven and Earth. It is called the Rainbow Bridge because of its many colors. Just this side of the Rainbow Bridge, there is a land of meadows, hills and valleys with lush green grass. When a beloved pet dies, the pet goes to this place. There is always food and water, and warm Spring weather. Those old and frail animals are young again. Those who have been maimed are made whole again. They play all day with each other.
But there is only one thing missing. They are not with their special person who loved them on earth. So, each day they run and play until the day comes when one suddenly stops playing and looks up. The nose twitches, the ears are up, the eyes are staring, and this one suddenly runs from the group. You have been seen, and when you and your special friend meet, you take him or her in your arms and embrace. Your face is kissed again and again and again and you look once more into the eyes of your trusting pet.
Then you cross the Rainbow Bridge together, never again to be separated.
- Author Unknown