How crucial is trigger?

Dear Dr. Braverman
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.

I would certainly advise letting your IVF doctor make that decision and arrive in advance to let him make that decision. I typically see my patients from abroad or out of state no later than the 9th day of stimulation so I have a couple of days to make the decision on trigger.