I don't see this as cheating. Yes, your sim gets more time to do things, making it easier to complete multible aspirations, get to the top of their career and get some bonus levels, get toddlers that Top Notch Toddler trait, may out many skills and more. Long lifespan is simply normal times 4.
Benefits for me are that as I'm a rotational player who only has the active household age, I get longer time to play with an household and get less dramatic effects from CAS aging glitch. Though one disadvantage is that it can be too long. Adults and younger sims can be aged up simply with a birthday cake/age up treat, but if I want an elder to die by old age, I'll have to get the AllCheats mod and use cheats to do it (more annoying with pets as I have to get their SimID first and that SimID can't be copied).
Usually when I think about cheating, it's filling the needs to the max and freezing them that was, maxing out skills instantly, getting from career level 1 to 10 in a one day (+ 50 bonus levels for higher salary), giving your sim many beneficial traits and university degrees so you'll have to scroll a lot to get to the bottom of the Simology panel, instantly maxing out your sim's fame level or reputation ect. At long life span, you do have more time, but you still have to work towards happier and richer sims. So I don't see it as cheating. Rather I see it as a less stressful patience training.