Does anyone know if there is a warning before a new timing belt is needed?

Does anyone know if there is a warning before a new timing belt is needed?

Normally, no.
That is why there is a recommended inspection interval. If the belt has too many miles on it, there will be stretching and/or possible dry-rot.
If you don't know the age or condition of your timing belt, I would recommend having it replaced. Some engines will suffer very expensive and very extensive damage if the belt should fail while driving.
Peace of mind is priceless.

There's no warning. I recommend replacing timing belts every 90,000 miles or 7 years, whichever comes first.