In 2010, you came across a site that was giving away bitcoins. The site said it was free money so you signed up. You were logging in to figure out how it was money but couldn't. The last time you logged in you had more than 100 bitcoins. Later you forgot about the site until 2017 when a ponzi was advertising Bitcoin. Bitcoin? The name rang a bell and you stated hearing stories. You remembered you must have many bitcoins somewhere but you can't even remember the name of the site. How would you recover your BTC?
Maybe it is depends on the site. Must be very big site that still operate until that long. And for some site, usually in certain of year our account delete from their databases. For 9 years interval i think as long you still save your email, only email which still save at least website that we register. And we can start to recover it there. For some people,lose their email account sometime not really big problem because they can create new. When actually, email is important thing for something like this.