From culinary uses to cleaning and pest control, lemons are widely applicable in the home. But they do not remain fresh forever, and obviously, their usefulness is dependent on their shelf-life.
Lemon, in any form, stored in a freezer will stay fresh longer than that kept in a pantry or fridge. But no matter the method of preservation, they will all go bad after some time.
The easiest way to tell if fresh lemon is stale is to examine it. Naturally, the skin of a good lemon should have an even bright yellow color.
We all love that fresh, citrusy smell of lemon. But once you notice your lemons are beginning to smell fermented, rotten, and objectionable, they are bad and should be discarded.
If your lemons have a powdery feel, they are most likely already moldy and should be discarded.