AT&T data session length always around 7 hrs long

Why is it that the LTE-M data session lengths are always around 6-7 hrs? I am not sure if this is AT&T specific because I can only connect to AT&T.

We artificially cut all sessions at around 6 hours for billing purposes. It’s possible the actual session is sticking around longer (though sometimes the tower will cause a reconnect at some point.)

The SARA R410 will attach itself to the network by itself. Is anything required on the modem end when this 6 hr session is cut?

No need to do anything in this case. It’s not even a “real” disconnect in most cases that the modem actually sees. It’s probably just in the accounting.
In the case of a “real” disconnect like if the tower does request it, the modem should handle that by itself anyway. If you’re using PPP on your device you might need to restart it in that case, but it will usually try to reconnect on its own if it detects that the connection dropped.

Thank you