Tickets may be made available at any time. We can appreciate that this may happen at unsuitable hours but this is the only way to ensure that they're fairly offered to each person in the list.
The best thing to do if you miss your chance is re-add yourself to the waiting list.
NB. If you're notified between 10pm and 8am then your ticket(s) will be reserved until 8.30am. However, if you do click the link between these hours then you will have the usual amount of time to complete your purchase (10 minutes)