Just for reference, the Spirit commuter policy:

O. Commuter Policy
1. A pilot commuting to duty shall plan for a minimum of two separate flights that will arrive at his domicile in advance of his normal report time. If the first flight is oversold, delayed, or canceled, or if the pilot is denied a jumpseat or boarding for any reason, he shall notify Crew Scheduling as soon as practical.
2. Crew Scheduling, at its discretion, shall take one of the following actions:.... longer, but basically: buy ticket/assign later trip/put on reserve/release without pay.
4. A pilot who keeps accurate records of his scheduled commuter flights and otherwise complies with the provisions of
this commuter policy shall not be subject to discipline for missing trip pairings due to denied boarding.
5. A pilot may use the commuter policy as necessary with no limitations.

Obviously almost everything is better at UA. But I think as responsible adults there should be no reason to even worry about the CP as a commuter.