Closing the Deal

When does a friend with benefits arrangement expire? You and your girl are sitting on the bus stop when a sexy guy pulls up and wants to talk to you. You all exchange numbers and later you go on a date. The chemistry between the two of you is a sensual eruption. You two have sex and later it develops into a friend with benefit situation. This "friendship" last for years and then during this unorthodox courtship you meet another man and now you are in a commited relationship. Yet you never officially ended the situation with the "friend". Is there an expiration date on a friend with benefit situation?