I've been running FC IIs (285X75X16, 33") for 4 years, around 50.000 ks. They have seen mostly gravel and desert sand, with the occasional rocky bits.
The only issues I have had are, one tyre split around the bead, about 1/3 of the way around the tyre, one (a back tyre) lost a couple of lugs and was showing cracks at the base of a number of other lugs and its mate was also showing cracks at the base of a number of lugs. To their credit the local distributor agreed to a 50% credit on replacement tyres for each "damaged" tyre.
When replaced you could also see the old tyres had a number of small cracks running down the centre of the tread. Looked a bit like an old perished tyre. Given that the tyres had never been run flat, or below 18psi on sand, they looked like they had!