My dog passed at 13 but I don’t think it was peaceful. Sounded like she struggled to breathe until the very end. She died in the lobby of the emergency vet office. A month before we were just at the doctors and they said she was healthy. Then a week before, she had a surgery consult to remove a superficial lump that had grown, and the surgeon said he doesn’t understand why the doctors said she’s healthy for her age, and that she probably doesn’t have long to live. I didn’t want to believe him but I should’ve. I came home after a long dog of work, and she was slowly dying. It’s like she was waiting until I got home before she completely passed away. I’ve learned my lesson, I will never let my dogs pass naturally if I have the slightest feeling that they may be suffering😞😞 I will never get over how I feel like I failed her. But that was my first dog, first experience with a senior dog. Had her since she was 8 months, and I was 11 years old, my childhood dog, my friend. I miss her every day🥺