Parting with Transformers toys is something that I very rarely do. If I didn't want to keep a toy for keeps, then I just don't buy it in the first place. When I do offer a toy up for trade or sale, it's usually because:
1. I've come across a spare. <---99% of my trades/sales are because of this
2. I've come across a later version of that toy which makes the earlier one feel redundant. e.g. I sold off my Classics Megatron, Skywarp and Astrotrain after getting the Henkei versions.

So at most, I might experience, "I don't want this version of this toy any more," but never, "I don't want this toy anymore."