It's actually pretty easy to get to use Chieftan or Conqueror's skill twice in a match. You're pretty much guaranteed to get the chance to do it with good use of the Defense lieutenant skill as long as an enemy Seren doesn't show up in a bad spot.
The other re-useable skill, Fortress, has way too long a cooldown though and it's extremely rare to get to use that twice before the tank that has it dies.