Count the time you will actually set aside
Four forty-five-minute episodes contain three hours of video. With ten minutes between each pair, the session becomes three hours and thirty minutes. The final episode does not add another break. You can change all three inputs without choosing a title or creating an account.
Use a sensible average
Some programmes have almost uniform episode lengths. Others have a short opening episode, a longer finale or extended specials. Look at the durations shown by the viewing service before entering an average. For a more exact plan, add the individual durations separately and allow for the breaks you want.
This estimate does not measure playback. It does not include advertisements, loading, skipped recaps or the time spent discussing a scene. It also does not include sleep between several evenings. If the number looks too large for tonight, reduce the episode count instead of treating the result as a challenge.
Leave yourself a clear return
After the session, open the series and record the last episode you finished. The manual checkpoint will be there in this browser when you return. Keep longer programmes in My List, or choose a shorter run if that better fits your plans.