As far as I can tell, the only place it was ever released was on a bonus DVD with the RotK Limited Edition soundtrack (so not the normal soundtrack or the Complete Score).
I've been hunting for a copy of it for years but I've never found a good copy that I can afford.
I also really want to get The Music of the Lord of the Ring Films but that's stupidly expensive too! I need the Rarities Archive CD! I needs it!
Anyway, here's a history of Use Well the Days.