Here would be my suggestion for Southwest Lifetime status.:

Lifetime A-List: 1.5 Million Points
Lifetime A-List Preferred: 3 Million Points
Lifetime Companion Pass: 6 Million Points.

To the extent Southwest has the ability to look at old, legacy Rapid Reward segments = each segment is counted at 1,000 points. If you had a companion pass in the old system, let's credit that at 110,000 points.

All partner and credit card points count told the big number (let's keep the Rapid Reward partners happy).

What would be Southwest's incentive? Simple, keep high revenue flyers loyal for the whole year.

For heavy business flyers (i.e. I have already hit A-List Preferred and Companion Pass for next year - mostly on points from flights), it would give us a reason to stick with Southwest when we otherwise might be tempted to switch once we hit the major Rapid Reward thresholds. For example, until I hit A-List Preferred/Companion pass - I will fly WN from DAL to CRP, ELP and HRL. For the rest of the year, I will switch those routes to AA with non-stop flights (versus connecting in HOU to CRP AND HRL on WN).

If the lifetime milestones were in place, I would stick to WN on those routes all year long. (Likely a $3,000 to $6,000 swing, annually). Over the course of the time it would take for a flyer to earn the lifetime milestones - that is significant incremental income to WN.