Don't ask any questions...simply buy.
Over my many years of cycling I have tried out many tyres. I have always looked for a range of different reasons for my purchases - cost/weight/puncture protection/grip. Each tyre I bought would have some of the properties listed above, but not all of them. Some of them I would have a honeymoon period of a few hundred miles, then like a failing relationship, the shine would come off. More precisely they would puncture, tear or just have all the grip of a well oiled Turkish wrestlers, trying to take the top of a pickle jar. I'd cast them aside (mainly to the back of the garage) and off I'd go again - looking for the right match.
Then it happened.
By chance I was shopping on Spa Cycles and noticed some discounted Schwalbe Marathon Supremes (700c x 28). I bought a pair and the love affair had begun. I fitted them to my touring bike and with training plus the trip to Italy, covered over 8000 miles. I removed them from my touring bike and fitted them to my single speed commuter and they're still going strong. I was going to purchase a new pair for my new touring bike, but could not get any in a 28, so went up to a 32. These current tyres have done two tours, several winters and countless training rides. I have not utter a single cross word against them.
Like all great relationships, mine with these tyres is built on trust. I know that they're not going to puncture (as long as correctly inflated). I know they're going to stick to the road (as long as I cycle sensibly). They are simply the best. I'm accepting they're not the lightest tyres - probably not the choice of the "aero-set". However, for so many bikes these tyres are simply the best. If you are planning a cycle tour, need reliable shoes for the commuter bike, winter training bike needs new rubber - Schwalbe Marathon Supremes - the only tyre you'll ever need.