On the other hand, resell price of used devices isn't linear. There must be a sweet spot and I bet it is around 1 or 2 years old. Also there are externalities h

On the other hand, resell price of used devices isn't linear. There must be a sweet spot and I bet it is around 1 or 2 years old. Also there are externalities helping. For example, people travelling might resell abroad for better rates.