The biggest takeaway for audiences as they soak in NBC’s This Is Us is the element of emotional surprise.

And with the network announcing two more seasons today–a total of 36 episodes–the question is how long can this motif remain fresh.

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“Our theme on the show is how life will surprise you. We attack it as writers,” said creator Dan Fogelman at TCA today, “you can take your family and the revealing pieces of information aren’t necessarily that a young woman wound up with a different husband many years down the line, but it’s the order we choose to tell the story.”

While Fogelman wouldn’t reveal many details, he did mention two things about the future of This Is Us, “there’s a before and after to the family, there’s a hinge and it’s before and after Jack (‘s death — Milo Ventimiglia’s character). That will be interesting in future seasons to show where that hinge was slowly and surely.”

In addition, Fogelman mentioned that fans shouldn’t expect a spinoff series of This Is Us anytime soon.

“We’re still so early,” said the creator, “Rather than doing a spinoff, I’d rather keep it in the series at first.”

Fogelman referenced as an example Tuesday’s episode which took place before the pilot when the family’s three kids were born, and also featured Gerald McRaney as the doctor who delivered two of the them. In addition, there’s an upcoming episode that’s entirely with Sterling K. Brown’s Randall Pearson character.

Said the creator, “If well-executed, what would be a spinoff can just be done as an arc or a couple of episodes in our series. It helps make it so that the series doesn’t become the same thing over and over and over again and start boring the audience.”