Do they diminish older models

Ie I’ve been using 5.5 for awhile and happy with it. But in the last couple days it sounds very mechanical w repetitive phrases. I remember this happening w other models when the newer model comes out. Now 5.6. Has anyone else experienced this? Or am I imagining it? Bc now when I work w 5.6 it is infinitely better than 5.5, and that wasn’t always the case.