Questions about gauge size

So i'm working on a scarf that is VERY long and has an intricate pattern on one end. For that pattern to look right in the width I needed I had to use size 3 needles with size 5 yarn (it was the smallest I could get in the color I needed... =)

But now i'm done with the pattern and I realize that this is going to take quite a long time to finish knitting as I still have at least 3 feet to go minimum. I'm debating an idea of over several rows subtly and slowly stepping up my needle size to 5 or 6. But i'm not sure what that will do since i'm in the middle of this project.

Will it even help get it knitted out faster? I should point out that the rest of the scarf is just knit 1 row perl 1 row. So there's no pattern per se.

Thanks