Peering into the glass you should be able to see that the nail has changed colour. On closer inspection you can see that the iron nail now has a partial copper coating.
The lemon juice and white vinegar are weak acids, which is why the wait times are slightly long. If your acidic level is higher you may find that your wait times are reduced. The more oxidised copper you add to the solution, the more copper ions can be suspended in the solution.
Rinse off your nail and copper after use to stop them discolouring. Also don't forget to pour the solution away and clean the glass before reuse.