"Account email reverted to registration email"

I just noticed that one of my accounts has a recent history entry that says "Account email reverted to registration email 1 month ago" from an IP in a country I have never been to. Luckily the registration email is one that I control too. I have no idea how this occurred although I have an inkling.

The email was changed four years ago. So, I suppose the link that was clicked was four years old. What I'm getting at is: how come those "revert back to the registration email" links keep working after so many years? What would have happened if I didn't have access to the previous email and/or someone hostile had gained access to it and decided to keep the account? Wouldn't it make sense to have them expire after some time, say, a few months?