I don't have a whole lot of experience right now, as I have only done four pairings this year, but I can tell you what I have noticed.
I have a couple of males that haven't bred for me this year. I still have them, they are 09' bps and I figured maybe they just didn't care for the female they were paired with.
The 2 pairings I really cared about worked just fine, so I am content.
I have noticed, that some pairings just don't work out. I know that there are things you can do to get the males interested, but as I said above, was content with what happened without doing anything but switching males. Some pairings go quickly and work out great. Some just don't. You can't expect a snake to like any other snake that is randomly put in the tub with them lol.