what is the longest a project you have done?

Question: what is the longest a project you have done?
- Keywords:
  longest project
Asked by zoelewis13 to Josh on 7 Nov 2017.
- Joshua Hosking answered on 7 Nov 2017:
  
  A project I’m doing at the moment will last all year. We are designing busses for the island of Arran that will run on fuel made from poo so that no fuel needs to come onto the island.

Question: what is the longest a project you have done?