Can lemon juice concentrate be used after the use-by-date?
I also typically use bottled lemon juice, as my budget does not allow for fresh lemons. 

Stilltasty says you should use the bottle within a week, but I've had success with keeping it much, much longer. 

That said, this is one item that will not usually work well past its best-by date, I've found.

Maybe in the future, you could freeze it in cubes if you can't use it soon enough?