You are correct the service manual says to change it at 60,000 miles and does not give the option of mileage/time. But the top paragraph does state it may be necessary depending on variable conditions. I would consider a car sitting for a few years one of these conditions and fall into the "time" questioned point that is being argued. The belt will form some bit of memory from sitting in this position, and upon start up cause minor or significant cracks. Once the this happens the belt is now open for maintenance due to "time" and not mileage. Can you honestly say with all other points aside that it is foolish to change the belt no matter what age?
I do not fear what the future holds for me, I am not afraid to die.