Carly's Peregrine Dating Cliff Notes are very good ... and though we haven't seen point 7, things that we have seen could be points 1 through 6, they maybe only one of each. If Princess and Ivy are "at it", they have been very very quick - quick as in almost from the moment he arrived!! If they getting a "jump", they are ahead of schedule ... Princess' has been laying egg three progressively earlier since 2007 ..
2007 - April 27
2008 - April 23
2009 - April 22
As for how long will she wait for Trey - had a look back at the records and he returned on ..
2006 - can't find the exact date (yet) but I think end of March again
2007 - March 27
2008 - March 31 - this was the year Ivy came to visit
2009 - March 23 - ahead of a major US storm & about a week earlier than usual
So technically, he really late or not by much. I'm not meaning to give you all false hope, just a response to your question. Think about last year, there were a couple of abandonned nests when "old" mates reappeared. On the other hand, Princess could know something we don't ...
Technically, she can wait for another month without any problems raising their young before everyone needs to migrate - we had another year that was this late - fledging late July and all worked out more than fine if I recall correctly. Can't remember if it was a renest, could have been, but it worked out fine.