Exhaust abilities can be activated any time you could normally activate an ability.
2025-02-07
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.
2025-02-07
If an ability triggers whenever you activate an exhaust ability, that ability resolves before the exhaust ability resolves.
Haste
Exhaust — Tap another untapped Mount or Vehicle you control: This Vehicle becomes an artifact creature. Put a +1/+1 counter on it for each Mount and/or Vehicle you control other than this Vehicle. (Activate each exhaust ability only once.)
