I think I voted 10 minutes or less, but I can't really remember why.
However, I will defend my previous decision.
While having all the information spread out over two or three (or even six) ten minute videos is decent, and I DO understand Outpost 2 has a considerably steep learning curve (maybe it's the fact I started playing it when I was SEVEN but...), you have to realize the attention given to a thirteen year old game by someone who probably never really heard about it is not going to last for 20, 30, or even 60 minutes.
That being said, I chose 10 minutes simply because that's about all the attention you are guaranteed. Granted, there are going to be some people who will want to know what's under every rock and over every hill, but that's not enough to cut making a lot of videos if people are going to go "tl;dr" or in this case, "too complex, didn't watch."
Now, to summarize - and I do like the idea of multiple videos, don't get me wrong,
A single ten-minute "Here's the frosting on the cake" is great for your more casual gamer. Give them a basic introduction into the game, show them how some stuff works, but don't feed them too much. On the other hand, if you did only several smaller videos, you'd have people forgetting what's in the first by the time they get to the last, or they'll just give up and, as I said earlier, "tc;dw" the whole thing.
However, what if you did both? You'd have a more casual "here's the tip of the iceberg" video that basically introduces people (and links them here) and then they'll get playing and "I wonder what this button does..." the whole thing to the ME[size=0] [/size]S hall and then come bother us for the complex bothersome stuff, and then you'd also have the obscenely spread-out multi-volume videos that would allow your more dedicated nostalgic person to learn about/get (back) into Outpost 2 without having to use the abhorred Search function.
tl;dr version: Make both one ten minute and several shorter ones.