I've owned an LR-308B since ~2007. I've not tracked the round count, but its fairly significant. No springs worn out yet. This is the first I've heard of it.
Welcome to the forum fireman43. Your DPMS is a LR-308. The AR10 is made by ArmaLite. It's a trademark name. It's important because parts on these .308 platform AR's do not interchange like a AR15.
As to the springs wearing out faster, HORSE PUCKY!
The RE, or receiver extension spring should not fatigue any faster in a .308 than in a .223.
The source of this was a small gun shop where live. I have fired about a 1000 rounds thur mine with no problems. I did not believe the problem was real but I knew some of you guys could back it up for me. It is one of my fav weapons to shot and I would hate for anything to happen to it.
fireman43, one upgrade you may want to look at is DPMS uses a AR15 RE and a shortened light buffer. Changing out to a .308 length RE, .308 buffer that's longer and heavier, and spring well give you a noticeable decrease in felt recoil.