I think that the Seth-Roberts books are the best in the field, and they aren't and can't be dated.
Seth teaches that there is no time, except as a camouflage in our physical reality. If there is no time, then Seth's teachings can't be dated.
On the other hand, it is true that channels, like Jane Roberts, inherently translate the blocks of information they get through their beliefs. This explains why honest channels, mediums, and other psychics, come with sometimes widely different messages.
I'm not familiar Gregg Braden. Could you write in a few words, if, and why, his book is worth reading? I just found a free pdf copy:
http://www.healingthroughself.co.uk/..._of_Belief.pdf
What is the source of Braden's beliefs? From the
amazon's reviews it seems that he compiled info from various sources. I didn't get anything about he directly accessing himself a source of knowledge.