A: To make it taste smoother. The farther your liquor is from 100% alcohol, the more this matters. That is, it will tend to make a bigger difference on 80 proof vodka than on 190 proof grain alcohol. I’ve done a split test to confirm this and I found the difference to be huge. It makes a big difference on pretty much any liquor though. Is it absolutely necessary? No.
A: Because I like what it does to the flavor. I’ve aged batches up to 2 years and it adds a smoothness up to about that point. It does start to go downhill after that point. It doesn't go bad per se, just starts to lose color and flavor.
A: It can rest a really long time. There’s nothing in it that would really go bad and I’ve tasted batches that rested for over 5 years with no problems. It does start to lose color and flavor after the 2 year mark though, and that probably depends on the storage conditions.
A: No. But I plan to try that and will update this item at that point.
A: Yes, plenty of them. In the lemon category, I've tried Ponderosa lemons and Meyer lemons. I've tried lime zest and orange zest, which is another type of liqueur called arancello. I've also tried others that I've somehow failed to post about and lost the reviews in the depths of my hard drive. I've tried grapefruit zest (yuck), blood orange zest (yum), and I have a pommelo infusion resting right now.
A: Yes. I've tried adding mint, even going so far as to attempt a mojito-inspired infusion. I've added lime to a lemon infusion, added vanilla bean, and even added way too much lemon juice to a batch. Perhaps the most successful test was adding pineapple to the infusion, which was delicious.
A: I think so. I've done multiple split tests with organic and non-organic lemons and find the organic variety to provide a better flavor. It's the outside of the lemon that you're using for this infusion, the part that is exposed to the environment and to any pesticides that may be used. It's important to limit contaminants and to remove any wax prior to zesting for limoncello.
A: Nah. Beer can go bad if you allow the temperature to swing too wildly and of course cooling wine is essential to keeping it in drinkable shape. The reason in both cases is because of fermentation and the fact that there are living organisms in the beer and wine. Too much heat and you kill the organisms and thus the flavor. Wine "dies" at around 86 degrees Fahrenheit and gets ruined. There's no fermentation involved in making limoncello and nothing living in there that can be killed, so feel free to warm it and cool it all you like.