I have just reached that point in my collection that I have begun to sell a few pieces. The motivation isn't money, rather it's a refinement of what I have in my rotation and which pieces truly make me happy. In that sense, the exercise of selling is more a reflection of what I've learned along the way, and a lack sentimentality tied to the piece itself.
Maybe this is what is referred to as "bonding" with the watch? I know the few that I have sold, and the couple I am trying to sell are all awesome time pieces, but fall squarely into that category. I have found that if there is little emotional connection, then it's also likely to receive little wrist time, so why not move it along to someone who will enjoy it more?
Now, obviously, is a strange and difficult time to sell any watch, but I don't think that any of mine qualify as "retired". As another posted earlier, the only watch(es) that I would really considered retired would be a piece that I love, don't ever want to part with, but is otherwise too fragile to be worn in any regular setting.