Can you really trust someone who has "dated" 3 other ppl in from the same chat room?

[Courty23]

My 16 yr old friend met a 15 yr old girl in a chat room he spends a lot of time in. She has dated 3 other guys from the same chat and he had dated other girls from chat room. He swears she is the girl for him after being together a short time. It kinda worries me how he puts so much faith into this situation. Am I just being a pessimist or am I being reasonable? How long do you think this will last and will he eventually learn his lesson? He has only dated online. Thanks