I have done it where I sewed the borders together but left the last few inches of each border open. Then I attached it to the top and attached each border in succession at the ends so That it looked just the same as though you had attached them one by one. I did not miter the corners. It took a bit of figuring on paper to figure out the length of each successive border but it worked just fine and it was sure a lot easier than attaching them one by one!

Wow ! Thanks so much for all these great suggestions, I will learn how to miter ASAP. I never even thought of some of the things you all discussed. That's what is so great about having this forum. Thanks everyone.

Add boarers after main is quilted
 

When adding boarders I do them after quilting is done. This way it's quilted through. If I want boarder quilted I do it before adding next boarder. It works great for me.

i have done as many as 3 borders to a total of maybe 6 inches, and always do a mitered corner. Once you get the hang of how to do this, it is fairly simple.

I recently purchased "Quilting for People Who Still Don't Have Time to Quilt" by Marti Michell from Amazon. She has instructions for adding several types of borders (1) traditional types before it is sandwiched and quilted, and (2) modified quilt-as-you-sew borders. In the number 2 method, instead of adding borders to the quilt the traditional way and having to squish the entire quilt through the sewing machine, only the patchwork interior of the quilt is quilted. After that section is quilted, borders are added to the quilt as you normally would except you sew through the batting and backing at the same time. She says: "The point is, you have to make a seam to add the border fabric to the quilt top, so why not quilt at the same time?" I haven't made any of the quilts in this book yet, but there are quite a lot of them I like and that are now on my "to do" list.

Great question Wanabee Quiltin! All of the answers are very helpful as well as the tutorial suggested.

Tartan, and others, have given you the best answer. I love multiple borders and just allow extra fabric to let me miter the corners for a smooth look.