While love spells might be tricky to cast successfully, distance is not a factor. Long distance love spells and similar charms, like attraction and fixation spells, work by making the feelings of love and devotion that are already there even stronger. That is to say, for the spell to work, the target must feel at least a little bit of love for you. That's why it's hopeless to try to make a stranger fall in love with you; it's just not feasible to manufacture affection out of thin air. No amount of voodoo could change it.