Private keys and control of your own wallet are forever for sure. I want to think that they wouldn't go anywhere, being the top #1, but it's always safe to be sure when HODL-ing.
I am not really worried that Binance will disappear overnight, but I understand what LoyceV was talking about. It's the regulatory frameworks that centralized exchanges like Binance have to comply with that worry me more than an exit scam or disastrous hacking incident. But no matter what happens, it wouldn't be the first time.
Most replies hint at that it's best to learn the proper ways to go about the seed and private keys. I wanted to spare my friend from that since he hasn't expressed a desire to ever learn it. I will probably just do it for him, and then it's up to him whether or not he wants to learn the ways of Bitcoin.