Rgarding Ukupanipo Hekekia, all merfolk have longer longevity than other sim life states, except Vampires of course.
In my very young for-building file, I used MCCC to check his lifespan lengths from YA to Elder. His YA (28 days) and Adult (42 days) were similar to non-occult sims.
His default Elder stage, however, is 48 days long.
As an experiment, I replaced his Glutton trait with the Active trait. His Elder lifespan soared to 70 days.
For the sake of comparison, I used MCCC on the Gen8 Mistura heir, Hiroki, aging him form a Day 35 Elder to a Day 1 Elder.
He has both the Active and Long-Lived traits. His Elder lifespan is 46 days (13 days + 33 bonus days).
Kasem Bunma has neither the Active or Long-Lived trait.
His base Elder lifespan of 13 days increased to 22 days when I gave him the Active trait.
I used to know exactly how many days each bonus (Active and Long-Lived traits) granted.
But I want to say here that both the Active and Long-Lived traits add bonus days that are a percentage of the default Elder life span (I think, but no promises).
Since the Elder lifespan changed from 10 to 13 days, I no longer know.
(P.S. MCCC is a little bugged at the moment. Instead of separate default Elder lifespan (13 days) and bonus days, all the days are lumped into a total value.
TL;DR: If your Ukupanipo has self-discovered the Active trait, his lifespan will be 70 days. If not, it's 48 days.
Also, you asked about my favorite spells and potions:
Fave Potions:
Potions of Plentiful Needs, Potion of Curse Cleansing, and Potion of Rejuvenation
(some simmers also like using Potion of the Nimble Mind to boost skill gain, but I never use it.)
Note: Potions of Plentiful Needs can be used to refill a Vampire's Thirst. This is something a moodlet solver cannot accomplish.
Most Used Spellslls
CopyPasto (natch), Transportalate (super helpful when gathering collectibles, and Homewardial (for taking multiple sims along to the Magical Realm).
I always disable Transportalate when raising small children. Nothing more annoying then a toddler finally locating her parent only to have the parent transportalate somewhere else.
These two spells I use most consistently; the others I use if a situation could benefit from it.
Like Delicioso when my sim or their toddler is hungry but we have no food cooked.
Inferniate if another sim is annoying my sim or Bugliate if we see something we want.