Kirk, I think your comment on the nail polish is one the spot. I remember reading an interview with Annie Proulx where she praises the attention to detail in this film, that made the scenes look so real and fleshed out the characters by humanizing them. Some of the details I remember her mentioning were the accurate accents, the dirt under Jack's and Ennis' nails in certain scenes, Lureen's mom's "perfect Texas hair", the way Ennis' skin looked wrinkled and flaky around the corner of the eyes - typical for people who work in the sun and wind; she specifically mentioned Lureen's nail polish in the telephone scene.
Jenny, you pointed out Lureen's teeth. Working in the dental profession, I couldn't not notice them, LOL, but I know I am weird about that, so I never said anything. However, I think you were quite right - the tobacco/coffee stains are another detail that contributes to the realism of that scene and makes Lureen a well defined, human character.
Even the difference between the way Jack and Ennis age is noticeable. Ennis' face is dryer and more wrinkled due to his work outdoors. Jack's face has less fine wrinkles - his work is in a more sheltered environment, plus his social status is a bit higher than Ennis', so he can take better care of himself.
Did anybody notice how, as Jack ages, his eyebrows get a bit closer to each other, with those vertical wrinkles between them deepening? Like someone who has frowned a lot over the years. I noticed that in many people who are either judgemental and negative, or go through a lot of heartache through their lives. We all know Jack was not the judgemental or negative type, so...