I have several .308 Winchester caliber rifles including a M1A NM, an AR-10(T) Armalite and a Remington 700 custom bolt gun, all over 25 years old. While I have .308 Winchester SB Dies I have never used them or needed them. I have loaded new brass, brass I have previously fired in my rifles and once fired GI brass I purchase from a forum member.
While the Competition Full Length RCBS dies are sweet neither those or the small base dies have been a must have for me. Some will argue the SB dies overwork the brass? I really can't say but I don't see it hurting to have a set.
Ron