Appts can be allocated to an Expired Case - EEK!

Can you please make it so that a Case cannot be allocated to an appointment date which is after the Case has expired?

At the moment if we rebook the client whilst their Case is active into a date when it has expired the Case is/can be allocated to that appt.

EG: The referral expires on 20/07/20. I book an appt today, 16/07/20, for 21 August 2020.
The Case will be expired by the 21 August.
However it copies over the Case/allows me to allocate the Case to that date.
(I assume that is because TODAY is within the referral period even though by the time that future appt arrives the Case is Expired.)

This makes tracking Cases more complicated than it need be and less reliable.