How exactly should trigger be given?

Dear Dr. Potter
You have been kind to answer my last question regarding fresh vs frozen semen. I hope, you can answer this question as well:
How crucial is it that the trigger is given on exactly the right time? Is it a matter of hours or days? Can you mess up the hole cycle if trigger is given a few hours to late or to early?
I am asking because I am wondering if my local IVF-doctor is able to decide when to trigger me, so I can fly out last moment before ER or do I arrive to my ER well in advance to let the doctor there decide when to trigger? I am doing IVF-PDG 1000 km. away from my home.
Thank you so much in advance.
Wih kind regards from Europe.

The trigger shot is usually taken 35 hours before your egg retrieval. There is a window between 35-42 hours before the eggs are released.

Thank you Dr. Potter. And can you please tell me when do you usually give your patients the Orgalutran to prevent ovulation? Is it a matter of blood level and follicle sizes? Some gives it day 5 of stims, some day 6 and some day 8. What is your rule?