There are (at least) four kinds of ultimates:
Ultimate Ultimates, like the unchanging beingness of things, are really just abstractions.
Relative Ultimates, like infinities and forevers, are not abstractions, but point to concrete things we can describe, touch, and delimit from other things.
Mystery Ultimates frustrate all our delimitations of things from things and show us that life can't be constrained by our language and just keeps carrying on carrying on despite all of our attempts to pin it down or describe it.
And Ultimate Experiences are experiential extremes of all sorts: of bliss, of nothingness, of suffering, of everythingness, and of flow being the primary examples.
All the ultimates have fascinating internal relationships with each other. And people concerned with any one of these might enjoy or find useful inquiring into each of these because they can all help address big questions in interesting ways.