If you do a lot more walking while carrying the rifle slung, you might consider one of the triple strap slings. When in the compact/short form, the sling is the same length as a sling you use to brace for shooting, but there are three straps that overlap each other. When you will be walking, or carrying the rifle, you let out the extra webbing, and the sling becomes two very long straps so you can put one over each shoulder allowing you to carry the rifle like a backpack. This wouldn't be any good for quick deployment because once you take the rifle off your shoulders, you have to pull the sling back to the short mode before you can use it to brace properly for shooting.
I found a sling like this years ago in a gun shop, and have never seen them anywhere since. Although it was only made out of 1 inch webbing, I thought it was such a neat idea that I bought one, and have made a number of them for many of my rifles. The downside is that for this system to work, you need to sew the two sling swivels into the strap. Then, it requires two sliders and a specific way of threading what is about 8-10 feet of webbing through the sliders and your sling swivels.