I play with custom lifespan settings that doubles the length of young adult and adult stages, and find that my sims are consistently at the top of their careers by the time they age to adult. I do have Nraas SP and have checked multiple times that the mods setting which adjusts job preformce to lifespan is set to true and that the affect active performance gain setting is true as well. I have also tried using Nrass relativity to slow down skill gains so my sims would stay "under skilled" longer, but apparently up to a certain point sims don't actually need to fill the skill requirement in order to be promoted once the preformance bar is maxed out. So once my sims reached a high enough level in their careers to where their skills were too low they would start to loss performance everyday and eventually get fire.

I'm wondering if there is maybe anyway, either with an Nraas or non Nraas mod to maybe set a custom factor to preformce gain, similar to Nraas relativity option to add factors to skill gain? Or at least if any one has any tricks and tips for slowing down the frequency of promotions?

On City Hall or an in-game computer,

NRaas > SP > General Options > Options: Careers > Options: Job Performance...
...Adjust Performance to Age Span > True (you have already verified this one)
...Job Difficulty Scale (default is 1, higher values will make career progression slower/more difficult)
...Stepped Job Difficulty Scale (makes the higher job levels more difficult to progress through than the lower ones)
...Adjust Active Performance > True

Thank you, igazor. Don't know why I didn't notice those options before.