According to Dr Peggy Rismiller's book, the mother echidna weans the young one by opening the burrow, giving the puggle one last feed, then abandoning it. The young echidna has to feed, protect, and establish a home range with no parental guidance at all. So when it is time for Fips to go, in about 2 months, I take him to a patch of bush, put him down, and that's it. Absolutely no parental care. 7 months and that's it, regardless of size.
In the past we would spend months training the echidnas in cages, getting them "used to outside" and getting the taste of termites. If the wild echidnas don't do this, then there is no point me doing it.