Make sure at the very least shes 24 months before breeding and also make sure you have liquid calcium on hand (it helps a lot, especially if they refuse food or are too lethargic to eat anything), also have at least 400-600 saved away for vet bills... I've had to take my female to the vet twice so far and each time was about 100 just for the exotic exam and fecal testing.
If you breed too early or the female doesn't have enough calcium in the diet or isn't fat enough it could be fatal. My female laid about 27 eggs and lost about 100 grams, it also took about an hour for her to lay them all. First two days she was lethargic and very hesitant on eating, but after a few more days she got stronger but it was very troubling seeing her act like that.
There really isn't a specific age to worry about eggs, some females never lay. I'd just watch her and if you see any constant digging get a dig box setup and put her in during the day so she can dig her burrow.
As for breeding make sure you have a place where you can sell the babies where they'll get good homes.
Also realize your going to have to spend at least 100 dollars each month on food, maybe 200 dollars each month depending on how many babies hatch. That is if you buy in bulk online.
You also have to keep those babies probably for 2 months at the very least... but 4 would be better as they would be less fragile and more well started.
Also 100-200 dollars a month would probably be for a single clutch of 15-30 babies... one female can lay about 6 clutches from a single mating, each clutch having 15-30 babies so lots of mouths to feed.