Pour one 750 ml bottle of Everclear into a 1-gallon jar.
Wash the lemons with a vegetable brush and hot water to remove any reside of pesticides or wax, unless you know that they have not been sprayed. Pat them dry.
Carefully zest the lemons with a zester or peeler. Use only the outer part of the rind. The white pith under the rind is bitter, and would ruin the limoncello.
Add the lemon zest to the gallon jar, adding as you zest it.
Cover the jar, and let sit for 10-40 days in a cool dark place. The longer it rests, the better. There is no need to stir — all you have to do is wait. As the limoncello sits, the Everclear slowly takes on the flavor and rich yellow color of the lemon zest.
At this point, combine the sugar and water in a saucepan. Cook until thickened, about 5-7 minutes. Let the syrup cool. Then add it to the gallon jar. Add the 2nd bottle of Everclear. Allow this to rest for a second waiting period of another 10-40 days, also in a cool dark place.
During this time, collect and clean various liquor bottles and vinegar bottles (that you will eventually fill with limoncello). Also plan to make room in your freezer for the bottles.
After the 2nd resting period, strain the liquid with a very-fine sieve or a cheesecloth to remove the lemon zest. Discard the zest.
Use a funnel to fill various bottles. Store the bottles of limoncello in the freezer until ready to serve.
Serve cold in very small glasses.