When I picked up an open box S9 from the local Best Buy for a shade over $200 last week, I had the chance to trade in my S4 Nike edition 40 mm. The trade-in value was $15. I decided to keep it for nostalgia. The S4 did a good job for several years until the battery life dropped to maybe 8 hours. Battery health was around 69% last time I checked. It's hard to appreciate the incremental changes unless you go several years between models, so that the improvements accrue.