The second book after the time jump was when I finally gave up on New Frontier.
I wish I had. I've stuck with it, but I'd recommend "Stone and Anvil" as the endpoint for the series. The NF crossovers since then have been good, but the mainline books never recaptured their momentum after the time skip. It just ended up adding more balls in the air to a setting that was already nearly past capacity. It's similar to my big problem with the headline Deep Space Nine books (there were a couple when, a hundred pages from the end, O'Brien would be mentioned as attending a staff meeting, I'd go, "Oh, right, O'Brien's back. I forgot," and then wouldn't be involved in the rest of the story, and I went back to thinking he was still on Earth or Cardassia).