I got a recommendation from an experienced tourer to switch to Schwalbe Marathon Plus endurance tires during summer and Schwalbe Spike something during winter. I like the Marathon Plus tires, despite them being a bit slow, because I don't want to get a flat in locations called no-where. I am not interested about product recommendations but rather how can I know a good endurance tire for a certain touring location? If you know that a road is poor for the next 1000 kms, is it a good idea to switch to wider tires with greater volume? Is there any objective way to test a tire in a random shop? I have noticed that sometimes some LBSs have old tires but time-to-time it is hard to say. So how can I detect a good endurance tires if my favorite tires cannot be found? By it I mean that I want more objective ways to select tires rather than just brand.
It's difficult to judge the quality of a tire hanging on a rack in a bike shop. Experience (including recommendations) is an important factor, since it takes 1000's of kms to put a tire to the test. When deciding on a touring tire, buy a set to try out pre-tour. You'll get an idea how they handle, how fast they wear, how puncture-resistant might be just by using them for everyday riding. Then when you're ready for the big trip, put a fresh set on the bike and save the worn ones for when you get back.
Certainly wider tires will help on rough roads. Thicker tires may last longer. For puncture resistance, stay away from racing tires and look for ones with a kevlar belt (or similar puncture protection layer).
If you know the roads may be bad, plan ahead and get a wider set for the entire tour. Don't plan to buy wider ones during the trip -- you never know what will be available when you get there. Conversely, if you find yourself having to replace a tire while on tour, your options will likely be limited. You'll just have to settle for what you can find. (I once had to replace a split road bike tire in a small mountain biking town but only one shop carried my size -- an off-road knobby tire. Still better than a split one!)
Two points to note when choosing an endurance tire are firstly the thickness of the side wall, since while touring you can easily get rock, sticks, nails, whatever hitting the side while you are riding. Secondly, you can "age" a tire a little bit by buying it before time, and placing it onto a rim with a tube pumped up to low pressure to help fill out the shape. After a month or so you will find that the tire has actually hardened a little, and will be slightly more puncture resistant.