I have many reels with agate line guides, with some dating back to the Roaring Twenties! Some of these reels show lots of wear to them in many places
except for the agates. Nary a line burn on any of them and I have a couple of dozen. In fact, I don't think I've ever seen even a photo with with a line burn in the agate, Cracks? Yes, but grooves? No.
That doesn't mean they aren't out there, just that I haven't seen them, and I have seen a lot of agates. Keep in mind that a lot of these agates went through the period of braided silk lines that would pick up dirt and routinely wear grooves in metal line guides and aluminum reel frames. But not the agates.
If you use them on your rod, they'll likely be the last thing you ever have to replace.
