[quote=@The Nexerus]
<Snipped quote by Aristo>

A few years seems more reasonable than a few decades. Maybe four years? Most of that time is spent in the stalemate after the initial Order invasion, wherein the Order occupied the portions of Iorica north of Dalion, and Vyddru occupied both the city itself and the kingdom's countryside south of it. 
[/quote]Decades of "war" is nothing new in the middle ages.
Most warfare took place as sieges which are gigantic waiting games in general so a war lasting for decades doesn't seem really out of place to me.
Here's a list for 15th century European wars:
https://en.wikipedia.org/wiki/List_of_conflicts_in_Europe#15th_century

Generally when two major powers duked it out that rarely lasted for less than 10 years.
That's just my two cents on the matter, though.