I'm definitely on the sloppy end with my loungewear, but I'm okay with that. Which probably goes to Diana's point about people who work out of the house all day being more likely to embrace full-on lounge when they can. And my lifestyle probably influences me here in other ways too (no kids, so no kids' friends or kids' friends' parents dropping by, not really in a neighborhood where everyone knows each other, etc.). Anyway, onto the questions:
1. I don't really have a regular budget for loungewear. I can go for months at a time without spending anything, but would guess I spend maybe $50-$75 a year on things I'm buying primarily to be loungewear. Which means mostly bottoms for me, since everything else tends to be stuff I've demoted. Or t-shirts I can't resist buying because they're funny or sentimental, although I should probably stop with these because I have a lot and really only wear them as loungewear. New stuff I get is usually just from Old Navy since they're cheap and they have nice soft jersey. I usually wait for a good coupon code, then replace whatever needs replacing.
2. I'm really bad at replacing loungewear. I'll add new bottoms when the old ones are looking ratty, but keep the old ones for a while just in case I'm really low on laundry or something. I also feel guilty and wasteful getting rid of loungewear if it's still in decent condition and isn't so ancient and stretched-out that it just depresses me. Which is really silly, especially if I'm buying new stuff once in a while anyway. I think I have stuff from 6 years back, easily!
3. My loungewear capsule has lots of variety to cover different kinds of weather. For bottoms, I have yoga pants, a few pairs of fleece sweatpants, a few jersey skirts, and even an old pair of jersey gauchos or two. I actually just got a pair of black knit harem pants from H&M, too. Not sure if I'll wear them out of the house, or just to lounge in. For tops, I have the funny/sentimental t-shirts, and also a bunch of tank tops and solid t-shirts I used to wear for layering when I dressed a little more casually. On top, I wear demoted cardigans if it's cold. I also wear demoted jersey dresses sometimes in the summer.
So hopefully I've made anyone who feels bad about their loungewear feel better. Whatever you wear, you're probably not as bad as I am!