But if you suffer from early spoilage, you might well want to look into sulphites. Yes, it's obvious, but why it's obvious may not be. Wine is made by taking a sugary liquid and fermenting it with the help of some friendly yeasts. Liqueurs on the other hand present a completely different environment. There is no fermentation at all, and no yeasts.
Yeast is the most persnickety part of wine.
It has to be coddled with the right percent of sugar in solution and the right temperature and acidity ranges, and it has to be kept well clear of oxygen. And when the wine is done, you've got to go to some great length to get rid of the yeasts so they won't make any more trouble. With liqueurs, acidity is completely unimportant, sugar is added just to taste, air is mostly no threat, and temperature is much more flexible. Naturally, the cooler the mixture is the longer it has to steep, and it's possible to have it too warm, but there's nothing that requires you to keep it right at 60, for instance. You just dump all your stuff together, let it sit for a while, filter it out, sweeten it, age it and bottle.