Curses, Technicalities, and Giving A Middle Finger To Death On Accident
Technically speaking, you don't kill the Heart at the end of GL+T, because revisiting the boss fight area shows it still moving and beating, just a less active beat. Perhaps i am just overthinking but overthinking is my middle name
So consider the following;
The curse isn't dead, just simply passed on to the new owners of the rings, aka our two favourite husbands (side note: who are coming up on their one year anniversary too!)
Or maybe, the curse is only activated consciously. So, simply put, if they were to want to be immortals (more than they already are, being Mr and Mr "I got shot but like its just really mildly annoying"), they could.
You'd think that maybe the "curses" on the townsfolk are merely put in place to keep the residents stuck on the planet, a fail-safe provided by the Olmsteads. But the people are clearly still suffering from said curses by the time you rid the place of Eleanor and Vincent, something you can see by just attending the reception afterwards, or even just helping Burton after completing the main missions. They seem to be persistent little things.
And please, one "curse" directly targeted at two individuals at a time, which has the ability to hold one person's entire being (personality, thoughts, etc) in a ring until they are passed onto a new vessel and reborn as themselves again, taken DIRECTLY from the heart of the IMMORTAL GIANT MONSTER, you are telling me some vault hunters just killed the couple who made it and it went "yeah ok bye bye"??? The rings are still made from the heart, and I am doubtful that killing the people attached to it would harm it (since it is, again, seemingly still alive).
Wainwright may have called them "just some fancy piece of jewelry" but odds are they got an immortal tool on their fingers right there. He said "til death do us part" but I think that is farther away than he realizes
Or you know...The rings are just...useless jewelry now and I overthought this whole thing. That is probably it