Pretty much all the serious cycle tourists use the Sugino XD (500 or 600) square taper crankset. They last a long long time plus mated to a good square taper bottom bracket will give great service life. 110/74 BCD is a good setup to get custom chain rings. Mountain cranksets are designed to be stiff for drops and mountain riding and are not meant to be used or expected to be used for long distance touring. Not to say you can not use mountain cranksets, but there are better cranksets for touring but just without the bling bragging rights.