My personal opinion is that there is a big difference between old and new tire, regardless of the type.
Old tires typically are worn out and have a flat spot. When you put ANY new tire, there is a big difference.
I throw away tires much before they are worn out because they become square, while there is still 50 % of usable thread left.
On big bikes, this difference can be felt even more. When I had Kawasaki, the touring tire would last 15.000+ kms but I would change it every 10.000 because it would not go into curves... it tended to go straight.