My camera bag has two positions lens facing upward or downward. Most camera bags will have this position when mounted on your shoulder. I am attaching a picture of mine:
So like most camera bags, either my lens will creep down or creep up because of gravity when walking. The creep is not important when the bag is at home or in a studio or in the back of the car. While walking long distances however, this can be significant. So what trick do you use to have minimum stress on the lens?