Thanks for the quick responses!
Have you ever given any consideration to allowing trial players to play a full length game when hosted by a person with a key for LAN only? I can understand not wanting to allow them to connect to an internet game with full access, but in a LAN setting I don't think it would be as likely to be abused. I only ask because I enjoy getting friends together occasionally for LAN parties, and would love this game to have a place in them. I'm sure my friends would enjoy this game multiplayer, but I don't think many of them would play on their own (or even online), making a purchase unlikely. I know that there have been several successful games in the past that have supplied a free multiplayer client (no hosting), so there is some precedent for this sort of thing. The three hour point seems to be right around when the game starts to really get interesting (which is great for generating a desire to purchase btw), but a game limited to that point really has no place at my LAN parties, it would just aggravate everyone! I really think this option could work to your benefit as I'm sure I can't be the only person in this situation, and it could very well expose people to the game who otherwise might never have been.
Ultimately I know that this is your decision to make, and I'm not one of those whiny people who will argue with a game developer who disagrees with me. I guess if it comes down to it I'll just have to buy a few extra keys to use when my friends come over.