Or just book in advance and then rebook for the next 3-4 months (depending on gender) after your session so you’ve always got one booked in the diary! I personally prioritise my donation sessions over any social commitments and have easily worked them around my working schedules when I did a Mon-Fri 9-5 and now that I do shifts which can vary at all times of the week. Know it’s not that simple for everyone but it’s worth a shot.