The whole message of the piece was that possessions are transient. You don't know if you are going to be able to have time with somebody, so you better be careful.
The kiss was the definition of perfect. True, it lacked the heat, the passion, the breathlessness of the living-world kiss she had given Milos, but this had something greater. More than a flash of fire, it had an unbreakable, perhaps eternal bond of connection. Mikey had transformed back into himself by the end of the kiss, and the moment their lips parted he knew, as he should have known long, long ago, that no one - not Milos, not another Afterlight, not anyone in any world - could ever come between him and Allie, from now until the day they met their maker.