What I like about Jane's story in Love and Thunder is that it's not her using the hammer to cheat death, but her using the hammer to make the most of the time she has left and die on her own terms.
In the Jane scenes at the beginning we're told that Jane is spending all her time in her lab and that she's hiding her cancer because she doesn't want to be treated differently. Jane is someone who has these great accomplishments and has changed the world and wants to do it again. She doesn't want to rest, she wants to keep going.
And being Mighty Thor gives her that chance, a chance to live her final days out without symptoms. A chance to keep going and to change the world once more.
She gets a chance to save the day in a whole new way.
She's always been full of wonder and she gets to explore new worlds again.
She gets to reconnect with the man she loves, fix things, and save him in more ways than one.
The repeated reference to the idea that you have to die in battle to get to Valhalla is crucial to her arc because that's what Jane wants, not to "go gentle into that good night" but to "rage against the dying of the light" (is it probably a coincidence that Jane references Interstellar which prominently features that poem? Probably. But it still works as a connection). Jane wants to go out fighting, whether that's in her lab or beside Thor on a battlefield, and that's what the powers enable her to do.
