Below are some use cases for Action Executions.

You could enforce a global "stop all EC2 instances in the evening" policy using Skeddly's "Stop Multiple EC2 Instances" action.
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Then, on an as-needed basis, you could create an Action Exclusion, without an expiry date, to exclude specific EC2 instances from that policy.

Again, you could enforce that development servers be stopped at 7pm using Skeddly's "Stop Multiple EC2 Instances" action.
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Then, if a team-member is still using an EC2 instance at 7pm, he could create an Action Exclusion with a 12 hour expiry date. This way, Skeddly will not stop the EC2 instance at 7pm, but will resume stopping the EC2 instance the following day at 7pm.

Normally, you may have a fleet of development servers configured to start and stop Monday through Friday. But what about those holidays on Monday through Friday when you don't need the servers started?

Create an Action Exclusion for the holiday days. This will prevent the servers from starting.