Where did you get your asset allocation? Did Moses bring it down from Mount Sinai along with the ten commandments?
My guess is that you will do more damage to your fixed asset allocation by changing your mind at some point in your life than will be done by your small cap becoming small blend. You also don't really know that small blend won't give you better results in the future than small cap.
My second guess is that the effect at retirement of using small blend rather than small cap will be less than the effect of foregoing one latte a day from now to retirement.
If you want to switch all your funds around, go for it. But do it with a smile!
In my case, I decided to go for simplicity. I too listened to all this small cap stuff around here and allocated some of my TC account to it. Of course it dropped like a stone, and is right there with all the other funds in three years performance (a great diversifier!). Instead of finding another small cap or going with small blend, I just added it to my Cref Stock. Plenty of old timers like me did just fine with only TIAA Traditional and Cref Stock, and it still isn't a bad way to go.