On a more serious note, I think long distance exercise makes me heavier. It depends on your body type but if you go long distances and long times your body can hoard fat to prep for these hardcore exercise sessions. I have switched to doing a shorter workout of 20 minutes on the bike or treadmill. The first 30 seconds of every minute is go as fast and as hard as I can. The second half of the minute is at a slow leisurely pace. Then torque it up again. I have noticed I have dropped more weight this way. It's intense and it's only 20 minutes.
I agree exercise makes you feel "good" and it is worth it. To deal with the boring aspect of it I listen to books on tape or CD you can get at your local library while exercising. You'd be surprised how many books you can get through this way.