Is it the weather? shipping question....

I had eggs shipped to me last year and by day 10, usually, half could be tossed. I candled last night to make room for a few eggs I got in the mail and other than the typical araucana loss I always have, my bator was still full! I had ordered eggs as I planned for quite a few to either quit or not develop. Did I just lose so many because I had them shipped in the summer? To me it seems so...I am also wondering if *girl* eggs are less heat tolerant and don't fare as well in the hotter temps, if maybe that could explain why I hatched so many roos of so many different breeds....
It will be interesting to see how many of each gender I get this time.
So now I have 9 doz eggs in my homemade bator
I will be so overrun with chicks