Are third-row seats in midsize SUVs usable for adults?

Sometimes, but often not comfortably. In many midsize three-row SUVs, the third row is best for kids or short trips, with limited legroom and a high floor that raises knees. Larger SUVs and minivans usually have adult-friendly third rows. The only reliable test is to sit back there yourself with the second row set where your passengers would actually have it, and check how easy it is to climb in and out.