I think it'd be hard to commit to chasing Lifetime unless you were in a fortress hub where you really have no choice of airline.

I think of my own trips *to* Seattle over the years...I've flown every major plus WN, YX/F9, and AS. Coming from MCI, traveling there for business many times since 2004 or so, it has ebbed and flowed which airline has the best connection or whether a nonstop exists at all.

Thus I have to think that your outbound options will ebb and flow over time depending on your destinations and which airline is strong on that route. Plus with all of the AS nonstops, I can't imagine committing so heavily to another carrier unless you really know you fit their route map well.