These are very short stories this show is based on. GRRM himself is the one telling them to adapt it accurately which means short seasons that dont have filler. Back when people used to speculate about future spinoffs, everyone thought the Dunk and Egg stories would be 2 hour films at most. No one thought tv shows because they are simple short stories. They aren't sprawling epics like the main novels.HBO is on some real a$$hole shyt.
and if they take the HOTD route, watch them try to stretch this bullshyt while taking off years between seasons.
And I doubt they take that long between seasons if only because the kid actor needs to stay a kid through the 3 seasons covering the 3 books.