Rulings

Multiple instances of ward each trigger separately.
If an effect causes Winter to become an artifact, its second ability will cause it to gain a second instance of ward.
Exhaust abilities can be activated any time you could normally activate an ability.
If an exhaust ability of a permanent is activated, and then that permanent leaves the battlefield and returns to the battlefield, it becomes a new object so its exhaust ability can be activated again.
If an ability triggers whenever you activate an exhaust ability, that ability resolves before the exhaust ability resolves.