I am always debating whether it is worth it. I fly AA the majority of the time and am a Platinum member. With the current bonuses for certain cities in Europe including triple mileage for top tier flyers, I could easily rack up 30,000 miles for a $380 fare to London for example but I don't think I have the time. Also, I would rather spend at least a weekend and enjoy a city rather than fly out and fly back. In the end, there has to be more than the mileage for me to do a mileage run.