As long as the fresh lemon juice is refrigerated the fresh lemon juice will last for 3 to 4 days before it goes bad.
You can place the fresh lemon juice in a freezer safe bottle and freeze the fresh lemon juice and it will last for 6 months to a year and sometimes longer.
But if you're only refrigerating the fresh lemon juice you need to drink it up within 4 days before it goes bad.
Always keep any leftover lemon juice refrigerated when not drinking it and the sooner you refrigerate the lemon juice the better off you'll be.
The longer lemon juice sits out the faster it can grow mold and bacteria and go bad.
But if you constantly refrigerate it then it will last longer.