I press all seams open , with the exception of paper piecing. In over 40 years of quilting , I have never had issues of seams opening or failing because of "stress". I can tell you the times I had taken some of my tops to the LQS , so many would comment And say "oh how to you get your seams so flat". When I flip the top and they can see the open seams , they are all so stunned , as so many are taught "always press to the dark". It is my opinion that is a old rule and has outlived its usefulness. It is also my opinion that pressing to the dark creates a ridge of sorts, at the seam . If you look at where clothing wears out it is often at that ridge wear the bulk of seams creates a friction point and the fabric starts to wear. Granted we don't wear our quilts, but the friction of the washing machine will first start to show the wear in the color at that friction point will start to fade. This is the result of the fibers wearing down, and ultimatley weakens the fabric at that point. Look at your jeans .. where are the first areas that start to wear down .. its at the bulk or any raised area of a seam that takes friction. Granted this is an extreme example ,but my jeans aren't expected to last as long as my quilts and is offered only as case for the friction on fabric that is often over looked and comes from use and from washing.