Performance issues while using shape builder tool to subtract shapes from a rectangle

I have a bunch of text and strokes I have expanded to form shape objects. They sit on a large rectangle. I'm using the shape builder tool to subtract the text and lines from the large rectangle. It takes gradually longer as I'm subtracting the shapes one by one, and illustrator eventually crashes. It's using only 1GB memory and 10% CPU (and no GPU). Why is this happening? Can anyone think of a workaround?