As far as I know the 10-hour time-out is in effect still. I haven't ever put it to the test.
The only other limit is a maximum size per post of 20,000 characters. Is it possible you exceeded that, Les? It's equivalent to about 10 pages in a book. Over the years, only a handful of posts went over 10,000 characters, the
longest being 11,191. And, no, it wasn't one of yours, Les it was from more than ten years ago.
I'd endorse Calilasseia's suggestion of composing longer posts outside the forum, in a file you can regularly save.