After all, certain properties may be essential at time t; though they don't remain over the entire existence of that thing. Similarly, certain properties may be deemed inessential/contingent despite the fact that they remain through many vicissitudes. A thing may remain the thing it is even though we've chosen different properties to characterise it with. In addition, my thing may “cease to exist” before your thing even if they're one and the same thing. In other words, my essence, E, of thing¹, may disappear; whereas your essence, E¹, of thing¹ may remain.
What could decide the matter? On the surface it's easy to show a difference of degree.