Always delete episodes you have already watched. Most apps (Netflix/Prime) have a “Smart Downloads” feature. When you finish an episode, it deletes it automatically and downloads the next one.
: Enable a "Download Season" button so users don't have to manually click every individual episode. Expiry & Renewal
has the most Originals (which are all downloadable), followed by Amazon Prime (which includes third-party content like Downton Abbey and BBC series ).