Answer
How long should a crowdfunding campaign run?
Short answer
Around thirty days for most projects. Campaigns raise almost everything in their first and last week, and the flat middle of a long campaign does very little except give you more time to lose momentum.
The shape of a crowdfunding campaign is consistent enough to plan around. There is a spike at launch from people who already know you, a long flat stretch where very little happens, and a second spike as the deadline approaches and the people who meant to back it finally do. Making a campaign longer does not add a third spike; it lengthens the flat part.
A deadline is doing work that a longer window removes. “It closes on Sunday” is a reason to act today; “it closes in ten weeks” is a reason to think about it later and then forget. The urgency is not a trick — it is the only thing converting people who are interested but not yet committed, and it is why the final days matter so much.
The exception is a campaign with a genuinely cold audience, where the first spike can be small and the time is being spent finding backers rather than converting them. Even then, the answer is usually to delay the launch until you have an audience rather than to run a longer campaign in front of one you do not have.
The other end matters as much. Do not launch until the page is finished, because the launch spike happens once and a campaign that goes live half-written spends its best day converting badly. Everything you would do in the first week should already be done on day zero.