The first episode of Downton Abbey: Season Five runs slightly longer than 69-minutes with commercial breaks, and is available to stream in HD quality where bandwidth allows.
By the way, signing-in to the PBS website allows you to watch Downton Abbey episodes in HD. To make things easy, PBS allows sign-in with Facebook, Twitter, or PBS accounts.
The eight-episode, fifth season of Downton Abbey previously aired in the UK last fall, beginning on September 21, 2014. On December 25th, ITV aired a 93-minute Christmas special titled “A Moorland Holiday.”
The fifth season of Downton Abbey on PBS’s website will expire March 15th, 2015.