Yep, I can imagine that 50 minutes 5x a week on just a treadmill is pretty darn boring. You're at Duke, right? I'm pretty much in the same place I think, regarding FEV1. When I discussed exercise with Duke pre-transplant, they said that they wanted me doing 20 minutes on the treadmill, 20 minutes on a stationary bike, 20 on a Nu-step, and free weights at least 3 times a week, preferably 5. Basically I was to go as fast and hard as I could, while keeping my sats above 90, and i could use as much O2 as necessary. So that's what I've been doing. Breaking up the official "hour a day" workout by doing 20 minutes on different machines really helps with boredom, as does having a workout buddy. Do you keep logs of what you do, set goals? Sometimes that can help. Music or TV can also be useful distraction. What is your maximum heart rate when you walk? That can be a good way to tell if you are pushing yourself enough, or too much.
Question for you. If you use more oxygen and exercise a shorter period of time, can you go faster, work out harder? The point of the daily exercise, as I understand it, prior to transplant, is to get your body (heart and major muscle groups) as strong as possible, so you can recover as quickly as possible from the surgery. In some cases where people have not regularly exercised prior to Dukes workup, it may improve FEV1 or FVC enough to postpone transplant. But in general, once your lungs are trashed in the low 20's, exercise wont help your capacity much, although it is great for clearance and improving QoL. The transplant surgeons I have spoken with were all crystal clear that the stronger I could get my heart and major muscle groups, the quicker I was going to get back home post-transplant, barring complications.
I dont if any of this helps, but if you're frustrated, contacting your Duke transplant coordinator is a good idea for suggestions. They're usually really helpful.