If you're sitting on a pile of frequent-flyer miles, it may get tougherto cash them in. Just as airlineshave reduced seating capacity afterSeptember 11, the number of seatsavailable as frequent-flyer rewardshas been cut. By spending moremiles, you can increase the numberof seats available. Don't convert hotelpoints to airline miles—they're worthmore when you trade them for lodgingthan when you use them for airlinetravel. To earn maximum usablemiles, try to use just 1 or 2 airlinesrather than many, which will diluteyour rewards. Worried about milesfrom bankrupt United Air? You'reprobably safe, but you might thinkabout trading those miles for freetravel sooner rather than later.