The ship can shrink as much as it can grow. If you replace a wooden plank on it, the discarded wood is no longer part of it. And if you disassemble it entirely, the "event" is no longer happening, and the ship no longer exists.
It's analogous to any other "real event" you might think of. If you have a party, it starts when people show up and ends when people leave. Guests can come and go all the while.
The point isn't to define a strict beginning and end, however. It's to point out that the ship isn't defined by its original parts. It's defined by the confluence of parts that continuously exist and are recognized as being a cohesive entity.
The ship can shrink as much as it can grow. If you replace a wooden plank on it, the discarded wood is no longer part of it. And if you disassemble it entirely, the "event" is no longer happening, and the ship no longer exists.
It's analogous to any other "real event" you might think of. If you have a party, it starts when people show up and ends when people leave. Guests can come and go all the while.
The point isn't to define a strict beginning and end, however. It's to point out that the ship isn't defined by its original parts. It's defined by the confluence of parts that continuously exist and are recognized as being a cohesive entity.