I have an 03 Alfa See Ya on a Freightliner chassis. The tires were weather checked after 10 years and 60,000 miles. Plenty of tread left but they made me nervous. I replaced them with a set of Hanc...
Just remember the old tires were 10 years old and stiff from age. The new tire are very flexible both in the tread and sidewalls. The new tread also has much more grip to the road than the old tires. You will feel a difference in staying with the same brand and model of tire as far as old and new tires.