18 years old summer tyres

I’ve been riding 18 years old summer tires since the last week. I’ve been looking at the profile of the tires since autumn and I’ve only looked at the profile of the tires at that time. It was okay. Now my workshop has pulled the tires on it. The mechanics came grinningly towards me and congratulated me on being of age. I didn’t know what they meant until they told me that the tires were 18 years old. They still pulled them on because the master me inte, they are fine: no cracks, good profile – just hardened. Well, now I drive the things. So far I have not noticed anything big, but it is already a murky feeling, when I know that the things are half as old as I am. On the highway I have also driven several times over 200. I only now through research realized that such old tires are not as safe as the master told me. Are there any clues that I should note if ic h driving with such tires? Will they still drive for at least a month before I will get new ones. I have my son with me every now and then and I don’t want any risks. If Master had told me this earlier, I would have ordered some of them, of course, but he just pulled them on and only then told me the age.