What has been the longest time that you’ve spent building a circuit?

Question: What has been the longest time that you've spent building a circuit?
- Keywords:
  building,
  circuit
Asked by SofaHedgehog to Giovanna on 9 Mar 2016.
- Giovanna Tancredi answered on 9 Mar 2016:
  
  Six months! I had a lot of failed attempts! You need to think that in order to build one from scratch it takes 3 days if each step in the process works. had some issues with a instrument used in the process that was not giving reproducible outcomes.

Question: What has been the longest time that you've spent building a circuit?