Tammara :- Going from what i remember they can fertalise the eggs for 3 - 5 days. They did my egg retreval on a Monday and then did the transfer on the Saturday so mine was 5 days.
How exciting for you.. Just make sure once you have the transfer done, rest. I took a week off work to relax and i honestly think this must have helped even just a little. I warn you the wait for the bloods after they do the transfer to see if you are PG is horrible its the longest 10 days of your life, But be patient, positive and relax.
I wish you all the luck in the world