So sorry about your longtime friend!
It's such a rotten shame that dogs do not live a very long life compared to humans. We have always had very fine dogs since a month after we married and that was over 52 years ago, so many. Even had several Siberians at one time and the sled to go with it. Never got to take them with the sled often like we'd planned and wanted to due to work careers and raising a family. Now we regret it!
We also get so incredibly attached to our many dogs just like you Ben. It's like losing a child almost when you feel you must put them down to stop their pain. They are so loyal to the end and never complain about pain like humans do. It still hurts every time we talk about the last 2 Siberian Husky's we finally just had to help them stop hurting. One was blind and had severe diabetes and the other got spleen cancer and just stopped eating and was wasting away and couldn't even stand up alone. They were very very special friends and companions for us. At least we will always have those fond memories but we'd sure rather still have both dogs in good health.
Our dogs always loved to boat, camp, travel, hug up to us, protect us when they didn't like something, NEVER pee or poop in the house anywhere as they would let us know if they had to go out even if you were in a very deep sleep. One even learned to speak several words at about 5 years old like: "I love you", "mama", and get this: "moron"! Also a few other words. We didn't teach her, our daughter did while we were on a 10 day cruise and she greeted us back with our dog saying "I love you"! It blew us away! She told us that when the dog would do funny things she would say "moron" to her and then the dog would repeat it. That was how it started. It was clear and sounded like a 5 year old child talking. Why didn't we think of that? Never been able to get any of our others to talk since but being Husky's, they do talk a lot in toned howls when we prompt them rather than bark which they very rarely do.
We now have a gorgeous Siberian Husky and she will be 2 on March 8. We're 72 and the dog is almost 2. So, who's going to last the longest? Will the dog have to bury us this time?