For the sake of being complete, I recorded
mezzes being overwritten by other mezzes. Each mez blurred the goblin, and that effect can clearly be seen as the goblin gives his agro message upon each new mez. This not only demonstrates the reliability of the memory blur aspect, but also the fact that the effect does not require time or wearing off naturally to work.
The effects are the same across all four (classic) mez spells used: mesmerize, enthrall, entrance, and dazzle.