[wingnut60]

Being a little picky here, but I believe the term for a substance's adsorption/attraction of water is Hygroscopic.

And over a period of time, some moisture in the air-filled portion of the fluid reservoir may condense and allow water to contact the oil. In the ten years I owned my '05, this never became a problem--never a concern with the hydraulic fluid, just the gear packs wearing out. I think I remember adding about a pint of
ATF over that time frame.
But I did have a ram give out while at Paul Cross's place and I am sure he had to replace fluid at that time.