In short- Benjamin Franklin effect is when you make someone work for you, which makes them invest time and effort in you. One of the explanations is that since they had committed this investment they are now more attached to a person.
So more time and effort you put into someone the more likely you are to get attached to them. Equally, the less other person has done for you the more likely they are to loose interest over time.
A good relationship is a balanced relationship but don’t start keeping score either, that is just annoying.