Making Liquers for Gifts by Mimi Freid
"Liqueur making is fun and easy and can be adjusted to your personal taste after minimal experimentation. Many people find commercial brand liquers too sweet; you'll have the option to adjust the sugar content and will find your lighter homemade versions just as tasty (sometimes better!) and a lot cheper too. Glycerine may be added if a thicker consistency is desired. It should be noted that the shelf life after maturation is six to eight months, varying with each blend..."