early bird bookings should be non refundable.

[Fox-Daniels0]

What's the point otherwise?

[Jessica-and-Henry0]

The reason many early-bird flight or hotel bookings are non-refundable is because they are cheaper - which is not necessarily the case for ABB bookings. And in terms of refund policy, if you were to have a strict policy it would not matter how far away the booking actually is. After the 48hr grace period, you'd always get at least 50% of the payout for cancellations. 

If you don't like getting bookings too far out in advance, you can always limit your booking window to keep it open only 3 or 6 months into the future 🙂