While season 7 will technically have fewer episodes than any of the previous seasons (seven episodes versus ten for the first six seasons), a few of them are going to be over an hour – with the penultimate episode over 70 minutes and the season 7 finale clocking in at 81 minutes long.
Also, while season 8 – the final season – will only have six episodes, each could be closer to that 80-minute length of the 7 finale. If that’s true, we’re going to be pretty close content-wise to the earlier seasons of Game of Thrones (many episodes have been ~50 minutes, so ~500 minutes of action per season – 6 episodes of 80 minutes would be 480 minutes)
Thought of another way, the season 7 finale will be roughly the length of a (short) feature film. And season 8 could be the equivalent of six feature films.