Superior Camouflage Question?

[Piecesxiii]

Sometimes when i cast superior camouflage it has a very short duration a minuet or even less but sometime it can last a whole run across multiple zones. the wiki says Superior Camouflage has a duration of 24min. Is this normal behavior for the spell? Does it have some kind of random timer? or some other reason to fade early. spell is cast by a lvl 19 Druid and it will fade with no interactions. I know its normal for it to ware off if the Camouflage character interacts with something or someone that is not what i am talking about.