In my opinion, there is a lot of mileage left in that tyre, certainly far too much to even consider changing them yet...... I guess it comes down to personal choice. Over on our side of the pond, we have yearly MOT tests, which are becoming stricter and stricter, and tyres are certainly high on the list of being checked for safety (and rightly so), but that tyre would pass without any problem. I would go on a few road trips before autumn arrives then check them again.