This is the best post Ash has ever written. :-)
Seriously, Lukas, awesome stuff. Timeboxing is great advice. Without even realizing it I was getting ready to let my Customer Development phase drag on later than it needs to be. You've inspired me to be focused, lay out some short, attainable goals, and execute.
Bravo, much needed at the moment.
The problem starts with how we come up with the original idea for the startup. We rely on messy inspiration, rather than ideation.
I like the 4 Actions Framework for coming up with innovations. It gives you a systematic way to approach, discuss, and weigh these ideas.