Frodo’s memories of Balin

[Alcuin]

“The Bridge of Khazad-dûm” begins,

The Company of the Ring stood silent beside the tomb of Balin. Frodo thought of Bilbo and his long friendship with the dwarf, and of Balin’s visit to the Shire long ago. In that dusty chamber in the mountains it seemed a thousand years ago and on the other side of the world.

As I reread that again today, I also reread my note in the margin. To simplify using Appendix B,

2942 - Bilbo returns to the Shire with the Ring.
2949 - Gandalf and Balin visit Bilbo in the Shire.
2968 - Birth of Frodo.
2989 - Balin leaves Erebor and enters Moria
2994 - Balin perishes, and the dwarf-colony is destroyed.
3019 - The Bridge of Khazad-dûm, and fall of Gandalf. (January 15)

So Gandalf and Balin’s visit with Bilbo, Frodo’s birth, Balin’s departure from Erebor, and the discovery of Balin’s are separated by twenty years apiece. (With a little wiggle room for Frodo’s birth. And the last jump is thirty years.)

Unless Balin visited Bilbo a second time before he entered Moria, and Tolkien failed to note it in his official timeline, “Balin’s visit to the Shire long ago” was not a memory of Frodo’s: his was a memory of Bilbo’s recollecting the visit, and possibly Gandalf, too.

Bilbo might have told of the visit several times: he was particularly fond of Balin, who seems to have been his favorite among Thorin & Company. Speaking to Frodo in Rivendell, he expressed disappointment that, “Old Balin had gone away,” when he visited Dale and Erebor. That must have as soon as he left the Shire, since Appendix B says

3001 - Bilbo's farewell feast
3002 - Bilbo becomes a guest of Elrond, and settles in Rivendell.

But it sounds as if Frodo himself recalled Balin’s visit to Hobbiton, not only on a first reading, but for many readings afterwards. Does this bother anyone else? Is it an inconsistency, or just something easily misunderstood in casual reading? Is it even an issue for you?