1. Very tough (and rather heavy). I did crash it many times and only managed to bend the sidestand (and tear it off). There are examples of Tenere's being hit from the rear by a car... but still no damage to the frame.
2. 450km
3. 73.000km before I sold it. Short circuit by worn wire (same as Niek), rear wheel bearings, hole/crack in silencer/muffler
4. true
5. Seems to work quite good off-road too, especially for the novice off-road rider
6. don't think so
7.every 10.000km
8. The plastic is very tough and robust. Even when you drop or crash the bike.
9. Suspension upgrade is always a good investment on almost every bike: the only way to tune it to your riding style, weight, usage (mostly tarmac or mostly unpaved roads)
10. XT660Z Tenere's have been travelling the world since it came out in 2008: it doesn't seem to be problem. You might ruin the cat when you use leaded fuel... but I don't think leaded fuel is produced/sold anymore.
11. check the stearing head bearings and cush drive rubbers. Not expensive to replace by the way. Ask / check the oil consumption.
12. Eats cush drive rubbers. Turbulence might annoy you.
13. Except for that one worn wire... no.
14. difficult, maybe only the gas tank (but no alternative available), wheels and hubs (check
www.off-the-road.de). Frame and engine are heavy, solid and therefore reliable.