That's good to know, 3 leisurely days for us - but that's a result of yhe distance we have to travel to get up there!
The gp4000s really do look nice, but they also look super slick whereas the 4 seasons look to have a little bit more tread on them.
My cross bike currently has thick 35mm cross tyres on, (plus a crappy 23mm rear road tyre for turbo) - so going to a 25mm super slick tyre is a big change! Whereas the 28mm 4 seasons seems to be more of a halfway house (at least it does in my mind anyway! )
Maybe I'll try to see both tyres in the flesh to have a look at them first