Offset Doesn't Wrap

I'm trying to create wood planks and I have seamless tiling disabled because I don't want the edge of one board lining up with the edge of another. Problem is, when I'm using the offset component to shift alternating planks down, they no longer line up in the middle because offset is getting noise from off the image I started with, I guess. I noticed the default "!" doesn't loop around, either, however the 5 color gradiant does. Is there a way to make offset wrap around within the image I have, rather than getting off-image data?

Edit: Nevermind - got it. I just masked my offset into two halves and moved one up and one down, rather than trying to move it all in one direction and hope it wrapped.