Originally Posted by MDtR-Chicago

My opinion is different than most of the others posted. Hopefully it will be taken in the spirit in which it is offered:

I don't think you should bother with any of this.

There are only two types of people for whom the active pursuit of mileage makes sense, and you don't seem like either:

(1) Those who have a low income level and could thus never afford to travel well otherwise.
(2) Those who enjoy some element of it as a hobby.

For everyone else, there is a higher financial and/or emotional payoff to investing the time elsewhere. Say you really invest yourself heavily into FF miles, keeping up with FT and booking complex award tickets. Your "return" on that effort, above being a completely passive earner, might be $5000 in real cash value.

Could you earn $5000 more investing that time into your career? Could you derive $5000 of value spending that time with your family? Or a hobby you actually enjoy?

I'd suggest you sign up for one program per alliance - whichever is easiest, so likely UA, AA, DL. Credit every flight you fly into whichever will accept it. If you end up redeeming miles later, think of it as a pleasant accident. Maybe, at the most, stop by FT every few months and sign up for whatever credit card deal is hottest, that matches one of those programs.

Otherwise, put everything on a 2% cashback card and be thankful you didn't waste your time.