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.
Cause when push comes to shove you taste what you're made of
You might bend, till you break cause its all you can take
On your knees you look up decide you've had enough
You get mad you get strong wipe your hands shake it off
Then you Stand
I saw my first lock with one girl on 2-10-2008 and she laid eggs on 4-25-2008 so thats lock, OVY, POS and lay in that amount of time. Then I have one girl that has locked 15-18 times and she is still building and glowing. So it all depends.
When you've got 10,000 people trying to do the same thing, why would you want to be number 10,001? ~ Mark Cuban