Do not assume that 25,000 miles is enough for a free flight. It is when there is availability, which seems to happen in the dead of winter between Cleveland and Buffalo. With United, when you want the award it may be 50,000 miles instead of 25,000 miles. Northwest is now adopting the Delta three tier scheme, so it might be 25,000 miles, it might be 40,000 miles, it might be 60,000 miles. Don't believe the 25,000 marketing hype, the reality is often different.