Edit: I think a balloon is a better analogy - most of the stretching happens when it’s almost full. But once “stretched”, there’s no need to deflate, as you’d just need to inflate/stretch again. Or you’d set off on a journey with a partially deflated balloon.
It’s like a water bottle connected to the tap. Once it’s full, it’s just hanging out waiting to be used. All the water is coming from the tap, the bottle is just sitting there with no wear and tear. When you disconnect, the water comes from the bottle.