I'm keeping all of my drones for 2 main reasons mostly due to the unknown whether they will ever be widely available in the future: 1. If one of my drones breaks down and I can't get a repair or replacement, I'll have a suitable backup and 2. The market prices for used drones are higher but not to the point where I feel it is worthwhile to sell; I guess I'm trying to "sell at the peak" sorta like buying on the dip. Right now there is a lot of fraud (on both sides) because people are desperate so it's hard to sell online without elevated risk.
So for me, timing is everything. Plus, I have way too many accessories for my drones which makes them harder to give up because you don't really get paid for extra accessories.