Why not incorporate it into the main quest that time has ceased to pass in Arcadia? Women could have been pregnant for 50 years now, an old dying king could have decided he has had enough of being bedridden and would like for this curse to be over with - and have hired a hero from a foreign land to come rid the region of it.

Just an idea. Probably brings with it far too many practical problems to be worth much (what is the effect on the economy? on crime?) and if adom is anything to go by I'm sure the venerable Thomas Biskup has come up with far better storyline ideas by now. It does fix the whole NPC/Aging thing.