Does it make sense to replace just one worn bicycle tire? When fixing a rear flat, today, I noticed that the tread on that tire is very worn. (I have fenders, so I almost never see the rear tread.) Today's puncture was a sharp stone that had gone through the tread. The front tire, by comparison, looks much better, and I imagine it has rather more life in it. I can get a new matching tire for the rear, or I can change the front/rear both, which would give me more options, albeit at at least double the cost.
The current tires are Continental Contact 700Cx37 that came standard on my LHT. I've ridden them for three years, and about 7000 km (~4500 mi), mostly locally (non-touring). Today was the first flat I've had. If I change both tires, I might drop to something in a x35, or maybe even a x32, in the hopes of getting something a bit faster, while not sacrificing too much in comfort or durability. But if I'm likely to still get a few years on the good looking front tire, it's way more frugal to just replace the back with a new copy.