I can state with certainty, that in 10 years, it will be 30-40 years old!
That would mean, built between 1982 and 1992.
Right now, we are selling a lot of houses that were built in the '70's; mostly because there were a LOT of homes built in the '70's. That means that they are 40 years old NOW!
We will always advancements in Electrical, Plumbing, Insullation, Roofing, etc.
There will always be demand for repairs and updating.
Add to that; some of the most beautiful and expensive homes were built a long time ago.
So, Age will always be an issue, and it won't.