If anyone's considered touring on GP4000S tyres, don't. At least not on the rear. With two laden panniers I had three punctures on Monday.
If you're thinking "of course, they're not anything like touring tyres, he didn't really think that through and I won't make the same mistake" then you're right.
I bought a Continental Touring Plus on Tuesday and have only had one puncture since, and that was a pretty hefty piece of glass, and even then it only just got through.