In your stating that it's very adolescent is somewhat accurate but says nothing to the idea that what it is, is a need to be promiscuous and that's not something "natural" in any way. If a man loves a woman, the need to have sex with other women should not even be on their mind.

Red flag #1. he's already cheated on someone. So you know he's capable of doing so.

Red flag #2. He admits to wanting to have casual sex while saying he loves you.

This to me just is saying he is the type of man that wants to have his cake and eat it too. he wants to keep you as a so called lover but wants to play around in the field. There is no reason for you to think that this will ever end.

He shows signs of being an adulterous male. Do you really want to continue when he feels the need to find sexual satisfaction from women other than you?

As a 46 yr old male, I personally have no need to have sex with anyone to the point of needing it casually. I personally find it strange to want to have intimate relations with a female that I'm not involved with on a deeper level... I must be in a relationship first. Once in a relationship I have no need or desire to have sex with other women and this is not due to my age, I never did at any age feel the need for 'casual sex". That says more about character than it does about his age, maturity or even gender. Men don't all "need" to have sex with multiple women because they are male. that's just bullsh*