You can’t sell something to a million people and still own it.
Copyright is a gift, from us to them, to encourage new works, for us. Why would that mean some old fart gets to stop people making new stories for the characters they grew up with? They’re our characters, now. We bought them. That’s what the money was for.
And if thirty years of revenue with zero additional labor required somehow isn’t enough - oh well.
Can you imagine making your argument for any other industry? Why in the name of god would art be the place where doing real good one time is a ticket to retirement? Not farming, not medicine, not engineering. Homeboy wrote a song once, so he gets to ride the gravy train until he fuckin’ dies.