Nail retracted – from how much mm difference 2 new tires?

Hi, together, last summer I hit a nail in one of my summer tyres (255/30 R19 Goodyear Asymmetric 2). It only struck me when changing to the winter bikes. Of course, it has to be a new tire now. After searching through diverese forums, the majority opinion in such a case is for exchanging both tyres directly on one axle. However, the described tires in the forums were usually already older anyway, which makes the decision of course easy I have now caught it with relatively new tires. Purchased 04/2014 about 10,000km (wearing arm / many motorway kilometers) about 1 – 1.5 mm consumed Is of course annoying enough to replace such a new tire. And a 2nd, even good tires to exchange all the more. Costs would be 2 pieces incl. assembly about 400 EUR. Now the question is: How “wrong” is it if one would only exchange a tire? Do you remember this very much when driving behavior? What would you do?