Changes in training

My ultimate goal right now is to train smart. Following a 65 week training plan for Umstead 2010 was intimidating. I realize that is my most important race. But I have several races I want to do this year, all ultras. I was going to use those as training runs, and I still will. But I realized that I can still have fun with those, too. I still need to build my mileage efficiently for those, and work on nutrition, to be successful.
So after a lot of thought and discussions about my training plan, I have changed it (although I haven't written it yet), to prepare me for my first ultra in the spring: Buncombe Trail 34 miler on May 3. I have taken out my speed walk days, and turned it into cross training. Mainly cycling. And during today's long run, I made a decision to do something I never would have done before. I'm adding walk breaks into my long runs. I thought that it will break it up into sections. I ran for 28 minutes, then speed walked for 2. I drank while I walked. I repeated this cycle until I was finished with the run. But it also was easier mentally, knowing I was going to get a break soon. It's also a great way to practice my speed walk that I will need for ultra races. I might increase the break to 4-5 minutes for the very long runs. I noticed that my average pace did not slow down that much. I was able to go faster than normal when running. Of course that could also be the result of the killer speed work session I did on Tuesday. Who knows?
I've also been told another way to train for very long distances, is to run by "Time on feet". That sounds like a great idea, but I don't think I quite understand the concept. I know I slowly increase the time I'm running, and not judge so much by how far I've gone. I'm just not sure I understand how to increase the time, and then what do I do for the weekday runs? Go by distance, or time? If anyone has insights or advice, please let me know.
I had a good week for training. I felt tired at 5:30am Wednesday morning for my run, but I did speed work at 4pm the day before. Less than 24 hours later. My legs were tired. But my husband applauds my dedication. That's always really helpful.
Tomorrow is a rest day, and I will enjoy it. Besides, I get to watch a bunch of guys run around a football field.
Happy trails,
Cheri