@Ynse-Yke0 Keep it simple, keep it straight. No doubt about it, this was an early check in request. It just so happened that the hour they wished to arrive was late, which only catapults the request further into ‘inappropriate’ territory. Airbnb hosts are people with lives, not impersonal hotels, with 24 hour front desk service. But even hotels have a limit to what they will accommodate, and there is a cost involved. By all means, be personal, pleasant and accommodate what you reasonably can, but see what you do as a business, and define and clearly communicate your boundaries.
People have a responsibility to familiarize themselves with the details of the Airbnb they are booking, to plan accordingly, ask questions and communicate plans to the host in a timely manner. It doesn’t fall to the host to scramble and pick up the pieces when that fails to happen.
You might consider addressing check in deviation requests in your house rules. Outline your rules, and charges. House rules should be strategically crafted to not only inform, but to act as leverage when needed. After all, guests attest at booking that they have read and agree to your house rules. If you haven’t, also set an end to your check in time, to cut off requests to arrive at very late hours.