Lemon juice will last for up to 3 hours out of the refrigerator at room temperature.
If you're not gonna drink the lemon juice or serve the lemon juice within a few hours you should refrigerate it.
After 3 hours of the lemon juice being out at room temperature it goes bad and should be dumped out and not drank because it could make you sick.
You can also freeze lemon juice in freezer safe containers to make it last longer.
Frozen lemon juice can last as long as 1 year before it goes bad.
But lemon juice will last for around 1 to 2 weeks in the refrigerator.
I buy lemon juice on sale and then freeze it to have it for the next summer or when I want to drink it or serve it.