Most flights that I have booked greater than 120 days out have some sort of schedule changes/problems that take as long or longer to straighten out than the original ticket took to buy.

Most notable disaster: I spent $1700 on 19 one way tickets on UA for 67,000 qmiles for 1K MRs scheduled in January 2005. With 3-4 legs on each one way, and putting flights as close together as possible to avoid long layovers, even a SNEEZE can cause re-booking issues. On the FOURTH time I was told yet another flight had been cancelled and I had to move several hours earlier or several hours later, I gave up and asked for and received a complete refund for all 19 one-ways (somewhere around 70 segments). I was stuck with a $5 Expedia service charge I could not get waived for the one flight I coudn't book on Unite.com.

It is REALLY HARD to get re-schedulers to reschedule a mileage run that yields Many miles. They always want to fly direct. Which defeats the purpose of the MR.