how long can a leopard gecko retain sperm?

Question
My female leopard gecko laid an egg recently, it had already gone hard when I found it, and a couple of years ago she had come into contact with a male, I don't know if they mated because I wasn't there. I was wondering though if it was possible, even a tiny chance, that the egg is fertilized? Also, is it actually normal for them to lay unfertilized eggs? If it isn't fertilized what should I do with it?     

Oh yeah! While I remember, why won't my gecko eat mealworms? She eats crickets fine. We just tried a swap cause they are noisy and escape, the crickets I mean.I am now feeding her both. Thanks :)

Answer
Hi Jessica,
Yes, they can and do retain sperm, but it isn't for years although on one site I remember reading they stated up to 2 years..but.. IO do find it hard to believe and some of thee other info there was not correct. Normal time frame to retain sperm is a breeding season..which, can be about 9 months. Is it possible that the egg is viable...anything is possible but the chance would be very slim. If the egg was moved/turned at all, that would make the egg non viable.
To dispose of it, regardless, we always recommend freezing the egg(s) for a few days prior to disposing of them in the trash, or even into the wild.  But, as I said, we always recommend freezing before disposing of them.
Leos can and do lay eggs without being bred but most times the leos don't.  Many reptiles do lay eggs w/o being bred.
She most likely doesn't make the connection of mealworm and food.  She is used to the crickets that give her chase and she has become spoiled on the taste of the crickets, unwilling to try a new food.  You may want to offer a few waxworms to get her on the idea that food doesn't have to jump!!.  Only a few waxies though as they can become quite fond of them and they are too high in fat content to be a regular meal. Be sure to gut load your mealworms prior to feeding them to your leo. Using greens, veggies, fruits, grains, etc to gut load both crickets and mealworms is the best...not the gel stuff they sell which is basically for hydration of the insects and can actually kill insects.  This happens when they insect eats pieces of the gel that has dried.  When the insect eats it, the gel re hydrates and basically explodes the insect.