the benefit is, quite frankly,
having sex on a regular basis without having to go find new partners constantly. i could pick up a different guy every night if i wanted to. but for various reasons, i dont want to. its a lot of work. you never know what youre gonna get with a random. it may not be worth it. you may regret it. its not convenient. etc. its a lot easier to just not have to worry where your next dick is coming from.
personally, im not a fan of sexual exclusivity outside of a relationship. i want to be free to feel like i can sleep with whoever i want. but this guy wouldnt have been comfortable with that. and since im currently more in the "its too much work" than the "i should sleep with whoever i want" mindframe, for the time being im going along with it.
idk. the last time i did fwb, we didnt say it had to be exclusive, and we ended up dating. this time the fwb is exclusive and i know 100% i'm not going to let it slip into a relationship. it depends on the two people involved how its going to work out. i wouldnt do this with a guy i thought i could be with.