I took the advice of Kickstarter, which stated shorter time frames are more likely to be funded. I crowdfunded another project (on a different platform) and one of the issues that arose was that those who pledged didn't want to wait so long between pledging and the money being taken from their account. As Kickstarter doesn't take the money until the goal has been reached, this means it could be a long time.
As a result, people waited until near the end of the project to pledge. Some may have forgot about the project in this time because of this. And it led to a rather stressful experience. 90% of my funding (yes i got funded) was raised in the last 3 days.
I do not think there is any point creating long project times. The reason I chose 4 weeks for the project is to cater for everyone's budgets. Some people get paid weekly, others fortnightly and some monthly. I am not asking for a lot for the pre-orders, so I think this is a manageable time frame and request.
I also wanted to make this project my birthday present :P