The length of the demo seems to be a really common gripe. You should address this as it seems to be putting off 75% of people who download it (well, 75% of the people who bothered to write a review, at least).
(and others)
If I wanted to fix this I couldn't - it's determined by the portals we publish on. They wrap it and set the demo timeout. But just because people are complaining about it doesn't mean it should be fixed - obviously people like the game if they go to the trouble of complaining, and conversion rate may well be higher. The portals test things like this because it makes a huge difference to their bottom lines, so I'm confident in their decision.