As jorlen was kind enough to point out below, the effect is Triggered, not permanent. Also, to reitterate another point by jorlen, having the advantage of Ultravision in places where inkies aren't welcome (i.e. Firiona Vie) is invaluble.
So even if you don't wear it in combat, it's a good item to have available, no matter your level.
Valaya Catstink
Barbarian Rogue, 48