Inside of combat, a class ability can only be triggered on your turn as an action. Exceptions to this timing will be prefaced with Interrupt and provide the timing for the ability.
Outside of combat, class abilities can be triggered at any time, as long as the ability makes sense to be triggered outside of combat and doesn't have timing specified. There is no limit to how many times you can trigger different or even the same class ability outside of battle - you are limited only by the amount of tenacity you have.