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"Stying 3 nights a week in a hotel."

For starters, insist on better accommodations.

If the fares are comparable and you do not mind traveling on regional jets, I would fly UA rather than DL. I think that you're more likely to get more bang for your mile with UA rather than DL.

If you can stay at Hilton-family properties rather than Marriotts, I would do so to double dip: Hilton lets you earn both points and miles on the same stay. And if you can change hotels once or twice on each trip, you can opt for the 500-mile minimum for each stay at a different, full-service Hilton-family property. (I'm not sure if United is one of Hilton's airline partners, but even if it's not, I'm sure that there is some United/Star Alliance airline partner that Hilton will credit to.)

Crediting car rentals to domestic airline programs is generally not very rewarding unless there is a significant bonus promotion being offered. When offered, you can usually find discussion of these offers right here in MilesBuzz! Absent a promotion, I usually credit my Hertz and Avis rentals to Virgin Atlantic: most rates earn 1,000 miles per rental (even a one-day rental), and there is no frequent-flyer surcharge when you credit the miles to Virgin Atlantic. Virgin Atlantic miles can be redeemed for travel on a number of airlines, including CO and US.

All of that said, I think that your best chance of getting enough miles for four tickets to Asia next year is to exploit the various credit-card bonus offers. If you can get approved for the Citi/AA Visa and Amex cards, you can get 150,000 bonus miles pretty easily. If you decide to concentrate on AA miles, credit your Hilton stays to AA, and save your UA miles for something else.

Good luck!