I've got some turnbuckles which appear to be chrome plated bronze and are looking questionable to me on the surface. I know the previous owner replaced all the standing rigging approximately 5 years ago, but left the turnbuckles in place. He had a professional rigger tune the rig when complete. Is it reasonable to assume the rigger evaluated them and deemed them sound in spite of the surface pitting? How long do bronze turnbuckles last? The pins have a W insignia on them, which I assume means they are original. I've got pictures, but don't see how to post them. 

Rich is right on.  Bronze is much preferable to SS
for all things rigging except wire rope.

Coming in late on this post, but there is usually no problems with the bronze center bodies of the turnbuckles.  The stainless threaded ends though, can have problems with crevice corrosion of the stainless.  They have to be inspected regularly..