dredgey,
So sorry to hear about the cancer in your Lab. Ours too was diagnosed with cancer in his right shoulder. Bailey is almost 14 yrs old and has had an issue with both of his rear legs; one had a cut ligament, the other a fractured elbow. So needless to say he's having a hard time getting around. He limps on his right leg and has trouble getting up but still manages to get about. If his back legs weren't so bad you'd wouldn't think he was really that bad. The docs gave him 3 months back in October 2010. He is on pain meds daily and really is doing remarkable considering all that is wrong. We've had him since he was 8 weeks old and is a mix Lab/Golden mutt (not pure breed breeding). His current bark is weak and the Vet said the cancer would spread into his lungs eventually back in October.
We keep him comfortable and provide the expensive meds daily to him. He's still eating well but has trouble sleeping through the night. We hear him attempting to get up and move around during the night time. He must be in more pain than we know. He's part of our family and is treated as such. I regret the forthcoming day when I'll have to make the humane decision.
Just do the best for your Lab and have no regrets - He Doesn't! Baily's Dad