Deciding whether a second location would solve capacity problems or multiply them

Customers keep asking when we'll open a second location because the current shop gets crowded at peak times. It's flattering, but a second site would mean another lease, staff team and supply chain instead of simply more sales. I'm considering whether longer hours, appointments or a better layout could raise capacity first. What numbers would you insist on seeing before treating ‘we're busy’ as evidence that expansion is wise?