It's always interesting when I crank up the speed on the treadmill. I never know how I'm going to take it, no matter how long I've been at the lower speed. Today, after about 10 minutes of bland 3 mph, I said, "heck, why not". I cranked it up to 3.5. It was nice for a while but after about 30 minutes I was like "yea, I'm not making another 30 minutes" so I went back to 3. I might start working toward 3.2 again but I think 3.5 is still a bit off. I hope to eventually get up to 5 and decrease my time on the treadmill (60 minutes @ 5mph ~= 90 minutes @ 3mph).
Course it doesn't help that the humidity in the room skyrockets while I'm on the treadmill. No matter how low it is when I get on it, my humidity/temp thingy says it's 60 something percent when I get off. I can pretty much handle any temperature as long as the humidity is low. 60 is not low.