For me the pivotal moment is Julia broaching the subject of treating Barnabas medically for vampirism. That put the imaginative twist into the story that got my attention and got my imagination stimulated, as a kid.
I think 1995 1970 and 1971 have awkward writing. It got childish and simplistic sometimes. Still, it would all have been fascinating if you'd never seen DS before. Anyone who hadn't seen 1795 or 1897 would have loved 1840. They got desperate and pulled out all the same old tricks to keep going, tweaking 1897 to get 1840, and it worked. That's what DC did, I guess, doing continuous CPR on the show to keep it alive. Barnabas's appearance came from that.
1840 was the right move. They were out of inspiration so they went back to historical atmosphere and a faster story, with all the elements that made the other past eras work. Things pick up an awful lot once 1840 starts. It was self-plagiaristic, but that's better than cancellation in 1970. It works if you manage to put out of your mind the fact that it's all taken from 1897.
If the Petofi period was within that "extension" of 1897 people are talking about, then I'm glad as hell it got extended. Every word I say here in praise of 1897 is based on the Petofi period, since my tapes begin toward the conclusion of Laura in 1897.