I lent one friend money to help pay for a video card and he paid me back exactly on time when he said he would. I respect him to this day. I lent another friend money to pay for some car parts and he did the whole dodging, partial payment, and then forgetfulness thing. I ended up giving up trying to get payment but wrote him off and never had a meaningful interaction with him again.
In some ways its crappy, judging an adult by something in their youth but I've yet to find a case where someone's character changes appreciably in this regard. You're either responsible and pay your debts or you're not.