"infinite lifespan" is a correct and usable phrase in written English.
You can use it when you're discussing an entity or creature that is believed to have eternal life, or to describe a long-lasting object or product. For example, you could say, "The legendary phoenix is believed to possess an infinite lifespan."
Her line, "an infinite lifespan with a finite memory makes for an awkward social life", is now almost up there as a catchphrase on a par with River's "Spoilers" and "Hello Sweetie".
With the increasing needs of clean energy, supercapacitors, especially the activated carbon (AC) based supercapacitors are attracting great attentions for their theoretically infinite lifespan.
(A3) Resting cells have an infinite lifespan.
These cell lines have an infinite lifespan and this, together with the fact that these cells grow in suspension, could facilitate vaccine production processes.
This includes altered cytomorphology, increased growth, reduced serum dependency, increased clonogenicity, a tendency toward anchorage-independent growth, changes in ploidy, tumourigenicity in nude mice and an infinite lifespan [ 19].
From a vaccine production point of view, the characteristic of continuous growth is beneficial, since such cells have the potential for an infinite lifespan, and characterized and approved master and working cell banks can be established.
In effect, they have infinite lifespans.
Mapped stars, like the mysterious island on which they dwell, mean many different things to many different people, taking on various shapes, stories and mythologies over their seemingly infinite lifespans.
Ashley points to a number of mistakes over the course of Infinite Crisis' lifespan.
Some time preference (σ > 0) for current consumption is sensible, however, even if just from the standpoint that lifespan is not infinite.
