That $200 pair of sexy panties you bought yourself will be used once, then reserved to only be used in times of extreme desperation. You quickly learn to categorize your washables into specific tiers depending on your sex life and laundry load.
We categorize our lovely skivvies by comfort and probability of getting laid. Unless you're one of those girls who is overly fashionable and insists on doing up-do's every day and thinks it's normal outside of LA or NY, then you've probably only worn your sexy panties a handful of times. You convince yourself it's because they require hand washing, and the French lace can't handle too much wear and tear. While this is true, it's BS. The F-ing things are more uncomfortable than those high wasted G-strings from the early 2000s (Whales Tail? I'm good, thanks).
Let's start with the most important and work our way down:
Spankies - These are the godsend briefs that are worn when we need a hug...or ass hug. This goes back to my FGP, they only feel right when they're over a true pair of Spankies. Just like my sweats, the majority of these I've had for many, many...many years. Unfortunately for us girls, they have panty lines, which is a flat out no-no in public, unless you're hungover or didn't care to get out of your sweats and desperately needed to go to the store for wine and chocolate (not just for PMSing). The male version is changing into a pair of white socks after being in their thin work socks all day. Unfortunately, this category get's a little muffled with the period panties. But that's just something we don't discuss. Like that Chick-lit (Hunger Games) you're thankful you're reading on your kindle so nobody see's the cover and realizes it's for teenagers. I guarantee we've all pulled the jam-and-cram trick and have tried fitting these under our tightest pair of jeans, out of pure desperation to give our cheeks a night off. Or we've already changed into our FGP, but have to go back out, and refuse to get back into a thong.
Period Panties - ...Since you brought it up. Each category has a pair of these, unless you're unbelievably good at managing your calendar. Others, count on their birth control pack to tell them what day of the week it is, and what time of the month it is. Let's just leave it at this: we don't have this down to an exact science.
HankyPanky's / Cosabellas - These are the thongs you wear every day. You have every color imaginable. No matter how careful you are with your wash, somehow every pair older than a couple months turn either into a blah-blue or muddled-salmon color. Those are designated for the workouts. While the newer, vibrant colors are your hot new Playboy Girlfriends that you strut around town with. Then of course there are the serious panties. These are the adult colors that you'd imagine Chelsea Clinton to wear if (god forbid) she had the same taste in dedicates as you. Typically stuffy colors like navy blue or hunter green.
Sexy Panties - It's possible a girl will wear these on a first date to make her feel good, but if she's worn them before, she knows that all night she'll be picking at herself like Al Bundy trying to position it correctly.
Realistically, she's wearing them on the ## date that she plans to put out. The only reason to wear these atrocious things is for someone to see them, take them off, and notice how delicate they are while laying on the floor. All in hopes that the sex-capade recipient realizes what a catch you are via a glance at your skivvies, and instantly asks for a deep, meaningful, exclusive relationship. <Insert whiny quote from Bridget Jones's Diary here>. Back on Earth, these panties are used in desperate situations (completely unrelated to sex). This is the phase after the workout panties and Spankies, but just before going Commando. I'm talkin laundry day.
Commando - I'm not a fan. So I am good about laundry. But this exists for casualties other than Paris Hilton and Britney Spears, or whichever young cracked out barely post pubescent celebrity girl is spreading it these days. Hannah Montana? Bieber?
Spanx - I was on a business trip a couple years ago with some of my work boys. They had never heard of Spanx (completely different from Spankies), let alone crotchless spanks. Probably one of the better conversations I've had. Definitely the best facial reaction's I've seen. Spanx are elastic cellophane that we use a shoe horn to shove our crevices, lumps, FUPAs and cellulite into. Acutally... they're the opposite of sexy panties. I promise she's not putting out if she's wearing these. If she does, then she shimmied out of them in the ladies room at the event you guys were at, and shoved them in her purse. Thankfully, the Crotch-Gods blessed us with crotchless Spanx. I'm not going into detail about this. But I can tell you...this is not something limited to younger girls. Mature women use these. I'll leave you with that image.