Over the years, I believe I've definitely had some reproductive issues caused by having female tityus mate a bit too prematurely. Even if they mate readily, it seems that if this happens too soon after becoming active, they do not produce fertile eggs. So, best to wait a few weeks after they have started feeding - a month, maybe. Of course, if you wait too long to mate them, they will loose reproductive viability. After becoming ready to mate, I'm not sure how long it takes for tityus females to become incapable of being fertilized - maybe 90 days?