Quality would dictate how long, IMO. Also, for this type of roundup, personally ...

functional-tree on June 12, 2010 | parent | context | favorite | on: Poll: How long should a weekly video summary of HN...

Quality would dictate how long, IMO. Also, for this type of roundup, personally I'd get more use out of an audio podcast rather than video. But regardless, I'd want it to cover stories well, whether that takes 10 minutes or 60.