We had the cot side cared to our bed, I the. Moved the cot to the nursery, and have a single bed side cared to our bed. The only time the cot got used after moving it was so Spock had somewhere safe to sleep for her naps, otherwise she was in the single bed in out room. And now she can safely get off the big bed so the cot hasn't been used in months. When it warms up I'm planning on moving her to her own room, and ATM the game plan is to just move the single bed. (Advantage with it is the legs fold down so is basically only as high as the mattress.
What I'm trying to say is we only really used our cot for a couple of months, even now if we did have another, I would only use it for day sleeps when they can move and don't understand the drop, and have bub with us in our current set up. Another thing I am likely about our plan is in that transition period, I can lay down with her in her room, which a cot I couldn't.