One morning after spinning class I asked Kim about how far we had gone, if we had actually been going anywhere. She said "about 15 miles, if you stay with me at the same pace I go." Of course I thought "WOW, I'm in really good shape. 15 miles already!" The problem was that I did not have a speedometer/odometer on my bike at home, so I didn't really know how far I was going.
For my birthday in November I bought myself a speedometer/odometer and put it on my bike. I took it out for a serious ride, the first time in months (maybe years). It was all I could do to put 6 miles on it before I got tired. My butt was sore and my legs were aching. Everyone tells me that it's not the miles but the seat time that is important in training for the MS 150. They say that your butt gets really tired sitting in that seat for 8-10 hr or however long it takes you to get to LaGrange. I believe them now.