If it downloads so slow that it takes longer than the clip shows for, then something's wrong. It means you couldn't watch it streaming in real time without it freezing regularly. Either your connection is shot to heck or their servers are overloaded, or your PC is doing more that it's sources can cope with. In your shoes I'd have cancelled, rebooted PC & router, and retried.
BTW one would upload to YouTube or download from YouTube. Saying, "downloading to YouTube", is rather confusing regarding which direction the data's going.