I don't know what service you are downloading from, but with Amazon Prime, and with Netflix you can set your resolution down to lower levels to save data. Also both allow downloading of much of their content, so you can download the movies, series you want to watch when you stop at a restaurant for lunch, use their wifi to download a couple of movies. I typically have 5 or six movies and a dozen or so episodes of whatever series the DW is currently binge watching on an old RCA tablet that we can connect to a tv via hdmi cable or from the chromecast.
