I noticed that in the book Through the Aegis, the Oracles of Didyma chapter, pg 97, they reference the Tessa and Damen Wards, which are ReCo(In) 60 wards with the Fire Duration (made by a Merenita). The main book also limits Fire duration to the forms of Ignem and Imaginem. Is there any official errata/translation/etc for this?
I don't think so, or more precisely I hope not.
Fire duration is incredibly powerful, one of the cheapest ways of making potentially indefinite duration spells. So limiting it to Ignem and Imaginem sounds quite reasonable to me.
I don't have Through the Aegis, but if I were you I would turn these wards into D: Until spells, with the condition being "while this fire burns", and you can get a legal workaround. If I recall it right D: Until is equivalent to D: Year (and, if not houseruled against, requiring a Ritual, but being a 60 level spell that's the case anyway), and D: Fire to D: Moon, so you will have to downgrade the spells one magnitude or make them 5 levels higher, but it would concur with Faerie Magic rules.
That was similar to my own line of thinking, and was the sort of errata I was hoping for. I certainly was not expecting an errata on Fire duration.
D:Fire spells must target a fire, and last until that fire goes out.
The corebook says that the Form of such spells is restricted to Ignem or Imaginem because they must target a fire.
Now, there are a few types of spells that target a fire without having the Ignem or Imaginem Form. For example, warding a fire against water is a Rego Aquam spell, even if the target is a fire. I would allow such spells with D:Fire, in that they match the "primary rule" (must target a fire) from which the "secondary rule" (Form must be Ignem or Imaginem) is somewhat carelessly deduced.
Initially, I thought that the wards of Dydima (I had not carefully read the chapter) were spells of this type: spells that warded barriers of fire from the passage of humans. But then I realized that they were not: fires in locked-away braziers are used as a "container" for indefinite duration spells. This violates both the letter and the spirit of the rules in the corebook, and is both unbalancing and "ugly". So indeed: poor editing.