I love limoncello, either all by itself or as the lemon-and-simple-syrup part of a cocktail such as an old fashion.
I use the Everclear/vodka version, but I kind of think the 3 months part is overkill. I’ve let it sit for 2 months and don’t really notice much difference from 2 weeks. In fact, if you don’t have a “zester” (a tool that avoids the pith in the lemon peel) the longer time will probably just extract more bitter stuff.
Anyway, what I wanted to add is that, while home-made limoncello is delicious and certainly cheaper than the bottled varieties, it’s still just limoncello. Why not climb completely out of the box and make it with bourbon? As ChuckMick noted, quality counts, so use good bourbon for this, not stuff you don’t like. Think of what you’d make a bourbon sour or mint julep out of. Maker’s Mark, all by itself should be great. Rare Breed or Bookers, with their flavor and color brought down to a more manageable level by mixing with vodka might be even better (never tried that myself, but I just thought of it).
The end product wouldn’t be a substitute for limoncello; it would be a different liqueur altogether. But it would taste delicious on a hot afternoon (perhaps in late June? Hey ChuckMick, are you coming?) right out of the freezer (no ice needed!).