Not trying to cause any problems here...

I've never been to a single pet store that housed every snake seperately. Never. It's a given that they don't do it. That being said... if they are indeed locking up, there is a few things to look for

1) Does the male, the one on top most of the time, have his tail to the side of the female and indented towards her?

2) If she blows up like a balloon for a few days, she's ovulating...DON'T TOUCH HER OR HIM!

3) After she goes into an extremely deep and long lasting shed, take the male out immediately. She will stress out easily from this point on out and it is important not to let this happen. Think of this as the first tri-mester of a human pregnancy.

4) From the date she sheds, 104 days should do it. After the shed takes place, up the temps so she is basking (her BODY heat) at 88.6 degrees.

Hope this helps.