Wow, 18! That's incredible! I was hoping to get there with my first girl, but cancer robbed us of that.
I've heard such differing life spans on Shelties, but honestly, there's never enough time. Gypsy was 15.7 when she passed in November, and my vet told me he was one of her oldest, if not the oldest, patient he had. (I honestly can't remember his exact words!) I remember meeting the vet for the first time in 2016, he had bought my retiring doctor's practice. He must've asked me twice how old she was, and then double checked her file. I was cracking up. She was a blue merle, so she never went gray, her colors merely faded, and even at that, it was slight.
That being said, she did have some health issues, like acid reflux and severe arthritis, but she knew what was going on until her last day. Then I knew it was time to make that decision. Luckily, I was in a place where I could be home and care for her in the few weeks after discovering she had advanced cancer. (Goes to show bloodwork doesn't always indicate everything!) If I had been working full time, it wouldn't have been fair to her. But she failed hard and fast, and I'm not sure if that was a mixed blessing.
I know my newest puppy's great-grandmother lived to be 15 or 16, and passed away a weekend after doing an agility competition! I found that crazy. She passed in her sleep, so I'm assuming it was a heart issue.
Does anyone think coloring or sex has anything to do with longer life? I know diet is a huge factor. Gypsy had homecooked meals from age 7 onward, due to her digestion issues and joint pain. (She had a gluten-free, grain free kibble as a snack so she'd leave my cat's food alone; he was addicted to it.) I feel like between that and supplementing her diet with fish oil, it truly extended her life for the better. I realized really early on if I wanted to supplement her diet directly, I could't mix it into kibble because she was a grazer. I'm a pretty strong believer in fish oil, I started my puppy on it less than a week after I brought him home. I plan to switch him over to 100% homecooked when he's older.