Probably a stupid question as I suspect I just want to spend money, but with my the upcoming Dreaming Tour, which will be a mix of bitumen and other "roads" and around 5,000 km in lenght, I am reviewing my tyre options.

Currently I have a set of Schwalbe Marathon Cross tyres which I used on the Esperance to Perth tour. These tyres have done 1,642 km and will probably do another 1,000 km before the big one.

So the question is do I fit a new set of Schwalbe Marathon Mondial Evolution the successor to the Marathon XR for the tour and relegate the Marathon Cross tyres to Extrawheel trailer duties or stick to my Schwalbe Marathon Cross tyres and just get a tyre for the trailer? Ideally I don't want to have to replace a set of tyres on the tour.

The Mondials are around $43 each from http://bike24.net.

The other advantage with the Mondial is that I can get them in 47-622 or 42-622. 47-622 might be pushing the amount of clearance I have with my SKS Chromoplastic P50 mudguards which are for 38 - 45 mm tyres. Will 2 mm make that much difference?

Thanks in advance