I started accruing miles at a time when a free roundtrip domestic coachseat"cost" 25,000 miles.Today, it maybe more (50,000 for no blackout dates) or lessdepending on thetravelseason andhow full the carriers expect a flight to be. Just as airfares are all over the place, airlines and other affinity programs are constantly tweaking the rules and requirements. I agree with omegaet--unless you're accumulating for a specific purpose, it doesn't pay to hoard given they're constantly getting devalued.
My strategy for airline miles: accumulate enough to be able to upgrade to business/first on overnight or long haul flights. I realize this is the same number of miles it would take to get a free coach ticket; but comfort and value trumps free for me--a free coach ticket with a $1,500.00 value versus paying the $1,500.00 coach fare + the $700.00 upgrade "co-pay" for a business class ticket valued at $8,000.00.
For points: accumulate enough to fund a weekend out of town (for a weekend in Atlanta we used credit card points fora freeflight in coachand cashed in hotel points for a free stay) or cash them for gift cards. As shygirl wrote, it's free money. You're almost automatically enrolled in the program anyway--use it!
I just checked out Delta for one-way tickets. They do indeed allow one-way travel, unfortunately at the full mileage required for a round trip. I plugged in my dates on a round trip basis and it would have come to 75,000 ff miles. With AA I got it for 50,000 miles with two one-way tickets. The saving is 25,000 ff miles... not too bad in my opinion. We have never done upgrades with our miles. I find Preferred Seating is pretty good in front of the cabin with only about 5 rows to the bulkhead.
We rarely use more than two cards (AMEX is our business card and we find their Rewards Program among the best and VISA through Marriott, since with the payment of a modest annual renewal fee, we receive a category 5 free night.
We recently signed up for an AA affinity card, which has an annual fee of $85, but grants 25,000 miles after spending $750 during the first four months following activation. Try buying 25,000 miles from AA and you will spend $625....this is easy math.
exflygirl, you got it right on points and miles. I consider these programs found money and try to use and spend them as would any asset. Sticking with the same programs has worked well and seems to have generated more extra perks along the way.