I'd suggest you do a lot of research. There's a lot of stuff out there and also on this site as well. One of my favorites is Markus Jayne's page. http://www.ballpythons.ca/gallery/breeding.html

You'll be more able to accurately judge the eggs arrival on other factors, but not so much on the date the bps actually lock up. Those factors are ovulation and post ovulation shed.

Be sure to research your incubation methods as well.