You may be getting mating without seeing it.
My rainbow boa's were going at it for a week or two before I actually "caught" them and that was only because I pulled out the moss box hide to get them out for feeding and when I pulled the top off there they were in the middle of a impromptu snake porno.
Have you seen any hemipenile sheds? That was the first confirmation of any sort that I saw. I found a couple of Hemipenile sheds in the water dish the 2 to 3 weeks before I caught them in the act. With snakes that spend less time soaking you may not notice the sheds since they will be smeared/dried on the substrate unless they come off in the water.
Sean.
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1.1 BRB
0.1 Pacific Gophersnake(unproven Hypo)
1.0 Amel Pacific Gophersnake
0.1 Striped Anery Pacific Gophersnake
1.1 Triple Het TPRS's
0.1 Silver TPRS
1.1 Amel Bloodred Corns
0.1 Abbott Okeetee Corn
0.1 Blizzard Bloodred Corn
1.1 Thayeri Kingsnakes
0.1 Reeve's Turtle
0.2 Amstaff's
1.0 Pudytat