True they well breed and lay eggs but the male can over breed her and she can get pretty hurt and she well beat your male up when shes not ovulating and your male wants to breed.
The problem with keeping a male/female pair together 24/7 is that egg production can be very hard on the female. Add to that a zealous male who is constantly pestering her, and you get a very stressed female who may not be able to maintain health and weight due to stress. Some males are less likely to constantly pester a female, some are very persistent. Either way, you will have eggs. And you will need to be careful to stay on top of the female's body condition and weight and supplementation.
That being said, keeping leopard geckos in groups of one male and multiple females seems to work out a little better since the male will bother them all equally, spreading out the "love." Again in this situation you need to monitor weights very carefully.
Personally, I keep all my leos singly, avoiding the issues all together.