I get 10,000+ per rear (150/80) Mefo Super Explorer- just keep the pressure from 36 to 42psi and they'll last- as per manufacturer.
Mefo fronts cup/wear funny (quickly), thin in the sidewall
TKC is good for offroad/mud but squares off fast on pavement (um, I corner hard & use my front brakes, a lot). Yeah, you can work around it most of the time but when panic stops are needed on pavement you're going to hate it- nevermind in the wet. They used to be cheap, but now they are premium priced. Not Recommended
Heidenau K60 Scout front is the ticket- great in the wet, strong tire/sidewalls, pretty good grip in mud (compared to all but say a D606) and you can fly on dry pavement
I have 2 (used) Pirellis Scorpion AT's in the tire rack, good rain tire for a lightweight dualsport but totally useless in the mud. Thin carcass as well. Think, "how to make your KLR handle on the street" but crap otherwise
As for D908RR's, they cost $$$ now and don't last. I'd go for a paddle tire for (dedicated) sand use, or go for a Terex. 1,000~2,500miles for a knobbed 908 is just silly unless you a)live in the desert or b)are buying it for a race/rally- it's WAY more important that the front tire sticks than the rear, sand is all about spinning the rear & keeping the front in-line anyway.
950 Adv 'S'
'87 KLR650 - +170K miles
"looks like you've had a lot of fun on that bike..."