Anyone offering me a swap to a middle seat from my window (or occasionally aisle) will get an automatic "No thanks - I don't like sitting in the middle seat either" response - usually that stops any further conversation dead! Only exception to that was if it was a middle seat in a premium cabin, and even then it would depend on the airline!
I'd consider an equal or better swap, but anyone asking me to downgrade has a snowball's chance in h**l of getting me to move....