Lust is often mistaken for love. The "falling in love" is purely a reaction in order to reproduce/mate and find a partner that will stick around to raise the offspring. When no offspring is on the cards, the brain shuts off those feelings and you start to look around for more suitable partners. The length of time can vary but generally three months is all it needs. This probably explains why people start going back to their usual bad habits after that time. Love is a subtle feeling that doesn't need a mating response. It develops from a bond that is created from memories and experiences shared. This is why people in love will often say that their partner is their best friend. It's effortless because you both have a mutual respect for each others happiness and welfare. You can be in love with more than one person because of these factors but who you choose to partner up with takes into account the lust factor, who can provide the best lifestyle, how safe you feel with them and the strength of the bond. I would say that I have never been in love, though I have been in lust many times.