I can't talk about inferior Ne and Ni without talking about their dominants: Si and Se.
Si-*-*-Ne
Si as a dominant function makes decisions and understands everything through how they've experienced things in the past. They have keen insight on small details of the world around them and are inclined either regard traditions highly, adhere to routine, or a combination of the two. As an internal function, this depends on how they've progressed through the world so far and Si is very much likely to draw from what they know. When presented with new amalgams they may ask, "Have I ever done this before? I'll follow the same way I did before." "Who's done this before me? If they were able to do it I can do it too by doing exactly what they did." They won't like it though. Si is inclined to stick to what's familiar to them. If possible they would avoid new frontiers. Ne as an inferior can serve the Si-dom to play out different alternatives in their head as a way to try to avoid them. In this case their inferior causes them to be paranoid and desperate to return to the world that's "normal" to them. "I want my life back!" Using Ne to the Si is not their strong suit and can manifest in inappropriate ways. Bogo from Zootopia, Toriel from Undertale, Li Shang from Mulan, and Gray from Jurassic World are excellent examples.
Se-*-*-Ni
Se as a dominant function enjoys the moment, the thrill, and what life has to give them right here, right now. In a perfect world the Se would treat itself to constant stimulation. Se is typically a very physically, robust person but they don't have to be. They can be inclined to crave only the finest venues and clothing lines and treat themselves decadently. They may ask things like, "What can I do with this opportunity? I want to experience life to the fullest." ((Ne wants to do this as well, but they want to experience everything they can consider whereas; Se wanted to just experience.)) As an external function, they make act first and think last because they're inclined to play with the world before pondering it and push to the limit. They treat opportunities and openings with steadfast interaction and can be their downfall. Ni as an inferior function can mean that the Se lacks foresight. Se's inferior function can be predictive, but it doesn't draw or dilenate their conclusions easily. They have a hard time either translating or implementing their own instincts or their gut feelings of what's about to come. As an inferior function, the Ni function can sometimes make an Se-dom feel aimless. However, when they do have a sense of purpose all their efforts and actions in the now are used to push to their abstract end goal. However, Ni-inferior lacks a cohesive step-by-step plan and only have a ways to just do. Deadshot from the DC universe, Mai from The Last Airbender, Han Solo from Star Wars, and Soos Ramirez from Gravity Falls are excellent examples.
I would argue that Se-*-*-Ni has a better proclivity towards immortality rather than Si-*-*-Ne. Se-doms are adaptable and would easily do so to the changing times and world that would definitely occur. They could easily survive like a cockroach. Si-*-*-Ne would put their efforts into either maintaining their sense of immortality forever ((if they were a vampire or such)) or implementing fail safes that would allow their world to remain prospectively the same as they know. They wouldn't survive the changing times and would always fight to maintain what is familiar.
