Jeffro
Post 1560
The letter of Jeremiah 29 was sent to those exiles in Babylon who had to remain there until a complete period of seventy years was fulfiiled for all of those people who would become exiled and in servitude to Babylon. At the time of writing that letter Jeremiah was in Jerusalem as the captivity had not then commenced. It is as simple as that. Jeremiah 29:10 does not refer to some partial or previous exile but to that exilic 'seventy years' where by the all of Judah was exiled, forced to serve Babylon leaving a devastated and depopulated land. A complete reading of Jeremiah proves this to be the case as there was more than one exile for the Jews.
It is not a matter of me making bold claims as you put it but that of simply reading God's Word and being faithful to it. We do not want to imitate those false prophets such as Hananiah but accept the prophecy of Jeremiah who clearly taught that the seventy years was a period sexile-servitude and desolation.
scholar JW