Introduction

When it comes to underwear, you want to make sure that you’re purchasing the best pair for your needs. It’s important to be mindful of the longevity of your underwear and when it is time to purchase new underwear. Below are some guidelines on when you should purchase new underwear:

When you wear a pair once because you forgot your underwear but no one sees.

If you wear a pair of underwear once and no one sees it, you may want to consider washing them.

You may have decided that life is too short to worry about having matching underwear, but if someone catches wind of your behavior, they'll never let go. Even if they don't say anything out loud, their eyes will be on you—and that's not something anyone should have to deal with.

To avoid this situation in the future: If you choose not to wash your underwear after wearing them once and no one saw it, make sure it's not soiled with any sort of bodily fluids or grease from foods that are normally eaten by humans (like tacos). This way there will be no chance that anyone can make a connection between those stains and yourself.

When you wear them to bed and have time to wash them before you wear them again.

If your underwear are the kind you wear to bed, then they're probably best replaced when they've been worn twice. When you wear them to bed and have time to wash them before you wear them again, this is a good sign that your clothing needs an upgrade.

When you have no other underwear available except for one pair.

The only reason you should buy underwear is when you have no other option. In other words, if you can't afford it or if you don't want to be caught in public without the undergarments necessary for the type of activity that requires them (such as going to work), then it's time to buy new ones!

When it becomes obvious that the elastic is stretched out, or the shorts have become too see-through for your comfort level.

You should replace your underwear when it becomes obvious that the elastic is stretched out, or the shorts have become too see-through for your comfort level.

Elastic can stretch over time. If you are not sure if your underwear is worn out, check to see if elastic is loose at the top of your waistband.
If a pair of briefs becomes too small for comfort, they may be more comfortable than wearing a pair that is too big and baggy (which can make you look outdated). But consider buying new ones instead as soon as possible because underwear that fits well will keep you feeling secure and confident throughout the day.

When the color fades.

The color of your underwear is a reflection of how well you're taking care of it, so when the color starts to fade, it's time to get new underwear. Some people think that if they buy darker-colored underwear, like black, they won't be able to tell when their undies start looking dingy and gray. But even black fades after repeated washings—and in fact may fade faster than lighter colors! “Wear dark colors at your own risk," says Jill McClain from Good Housekeeping. "It’s best not to assume that black will hold up better than white or other light colors."

The main way you can avoid having your underwear fade is by being mindful about where you put them in the wash cycle: never put colored items with white clothes! And try not to mix similar shades together (like pink with red). The easiest way? If you have an extra minute or two before starting your load, separate colored clothes from whites or brightly hued items from more muted ones so there aren't any awkward mishaps during cleanings.

When they are worn out by normal use, not due to a manufacturing defect or lack of care.

When they are worn out by normal use, not due to a manufacturing defect or lack of care. As a general rule of thumb, underwear is replaced when it starts to look old and/or raggedy. This may occur in less than one year if you wear them every day.

Only purchase new underwear when it can reasonably be expected that they will last a long time without wearing out

When it can reasonably be expected that they will last a long time without wearing out.
This can be hard to predict, especially for items like underwear. It's tricky because most people don't wear the same pair of underwear for years on end like I do (see: 4 years). If you're not in the habit of shopping for new undies every few months and instead use your underwear until they fall apart, then one way to tell if your current underwear is still good enough is by checking the elastic. If it has stretched out significantly from normal wear and tear, then it might be time for an upgrade!
Another sign that new undies are in order is if your old pairs are too see-through or have faded color over time. While this doesn't necessarily mean your underwear will fall apart after only a few washes, it does mean that you'll need something more opaque or bright if anyone else will see them under normal circumstances (aka when you're not alone with just yourself).
You should also take into consideration other factors such as poor quality/fit/materials; these factors might affect how long they last before needing replaced