Whilst not trying to defend Allhallows (club organising the event), race instructions normally only arrive 1 - 2 weeks before the event. Something we all complained about last year and aksed them to improve.
The delay is usually caused by the time taken to get approval for the course or from the local authorities such as the habour master. The harbour master regularly changes the course for safety reasons or other reasons such as anchored vessels.
I was told by Anne Robinson that the instructions are final (actually the same as last year), but as you know, they ALWAYS change, so please assume until you get hard copy they are still preliminary
I have already done my navigation based on the preliminary instructions and will tweak if I need to.