After your hackathon, it's really important to look back at both the positives and negatives of the planning process and event itself. Look at how you achieved what you did, and what mistakes were made.
It's important to do a debrief just after the hackathon while it's all fresh in your mind.
For the positives, write down how you achieved them so you can repeat this for your successor hackathon.
For the negatives, work out why they happened and if you can minimise the potential of it happening again. Mistakes are inevitable so don't beat yourself up about it. Documenting what happened will help everyone in the team understand how they can make the hackathon even better in the following year, especially if a new committee takes over. Last thing you want to do is waste time recreating the infrastructure that was created in a previous year, when you could be focusing on new and exciting things for your hackathon.