I've been doing some thinking about my SPH characters, now that a few years have gone by. Here's what I think they're doing five years out from Hogwarts graduation:
Seth: I think he took a mental health break after graduation and just spent a year learning and running the family business...while tracking down Zascha but not being very successful at that. After about a year, he applies to become an auror and is accepted, possibly with some reservations by the DMLE, possibly not.
The way I figure it, he and his friends can't retrieve Erzsebet until they find and secure Zascha. Part of the reason Seth becomes an auror, I think, is to get better access to information he can use to find Zascha. How he and everyone magick Erzsebet back into the present, I have no idea. All I know is that, if they manage it, Seth and Erzse will have to have a lot of very long talks.
If they never do find Zascha, Seth might, after a considerable length of time, start seeing a young woman named Morgana. If possible, I would like to think they all do something to help Nathan recover.
Paul: He has continued to use the Gareth Adams identity. Still married to Lilith, obviously. I think he has probably retired from teaching at Hogwarts, depending on how Voldemort dies in the SPH universe. I think, after the war, Paul will look for work with the Hawkwood Trust, if Lord Hawkwood will have him. As he says in my mind, "I do not wish to spend my life being some DMLE variant of 007."
He still acts as a father to Piotr and Sergei and cherishes his time with Seth--not least because Seth is blessedly normal. (g) I think Seth has figured out his true identity.
Mary Elizabeth: Has opened The Spider Pub in Knockturn Alley. But she's realistic about Greg and will keep him at arm's length if he truly is a dedicated Death-Eater after the war--'Cause her father would tan her hide if she weren't. :P
Daeren Alexander: Still a doctor and a healer, still working at St. Mungo's and assisting the Hawkwoods on the side. Still has not convinced Diotima Ridenow that she's too good for Lew Alton.
Artemisia and Petrus Graves: Retired to Iona and are living happily ever after.
Elizabeth Townsend Graves: She has maintained correspondence with Snape, if Snape is still alive in this AU. More than that is up to the two of them.