My X dropped at a fairly fast-ish rate, but stayed at 80% for like a solid 2 years. I finally went in to the Apple Store last November and said that and said, ‘I want a replacement, it’s at 80%, but I want it anyway,’ and they let me do it. YMMV, but for my (new replaced) X, I physically couldn’t drop it below 80%.
My X dropped at a fairly fast-ish rate, but stayed at 80% for like a solid 2 years. I finally went in to the Apple Store last November and said that and said, ‘I want a replacement, it’s at 80%, but I want it anyway,’ and they let me do it. YMMV, but for my (new replaced) X, I physically couldn’t drop it below 80%.