Pants Length & Heels? What is Wrong vs Permissable?

At what point do heels actually require longer pants length?
What can you get away with?

I can see from else where online what is supposed to be the optimum way the cuff should fall on the shoe. But my question is, "how much leeway is there in this?" Especially with off the rack pants, the tendency is for them to vary in length at 2" increments I rarely see the in-between lengths.

Is it different for jeans then slacks? If it is men's jeans instead of women's women's with women's heels? If the heel is a boot or booty? Chunky or block heels instead of narrow?

I have flats, 1 1/4", 1 1/2", 2", 2 1/2" & 3 1/2" inch heels, plus almost flats, which are mostly cross-trainers/running-shoes(sneakers) or hiking shoes with 1/2" to 3/4" heels (called drop for sneakers). Most of the pants I have are the proper length for my sneakers. Do I need different length pants for almost all of these? Without resorting tailoring that means I can readily get 2" longer & 4" longer. So.... How far off optimum length can I get away with before it is just plain wrong? What works OK with what?

Thanks for any input.
~Hypatia >i< ..:::