How far across London is actually worth travelling for five minutes?

I’m starting to realise a five-minute spot can quietly become a four-hour evening once you add getting across London, waiting around and getting home. I don’t want to become precious about travel this early, but I also don’t think every bit of stage time is automatically equal. How do London comics decide when a short spot is worth the journey — quality of the room, chance of another booking, how much you need to test the material, or just taking everything you can at first?