Turns out we've all been keeping our bras and undies waaaay too long.

It’s not just about how often you’re washing your bras. Turns out our trusty boob holders have a shelf life too.

If your underwear drawer is filled with bras bought before avocado became a brunch staple, you might be in trouble.

According to Daniela Hamman, Assistant Product Manager for Berlei, how often you wear your bra will determine its longevity.

“On average a woman will wear her favourite bra two to three days a week. If this is the case I would suggest replacing your bra every six months to a year,” she tells Mamamia.

Listen: How often should you wash your bra? Post continues after audio.

If you want to get more out of your bra, she says ensuring it fits perfectly is very important.

“When getting fitted it is advised that the bra is firm but comfortable at the middle hook and eye option. Once your bra starts to stretch over time you will then have the option to tighten it, increasing the longevity of your bra,” she says.

“Additionally if your weight fluctuates you have the option to loosen your bra.”

It’s the same with your undies – if you wear a pair once a week and wash them once a week, Hamman recommends replacing them every six to eight months.

Of course, it’s entirely up to you. If the colour is still looking good, they haven’t got holes and they’re still comfy, then you can (and should) wear them for as long as you like.

washing underwear
Image via Getty.

"If you hand wash your bras with delicate soaps or detergents you can prolong the life of your bra," adds Berlei Senior Technicals designer Lily Jong.

She also shared some signs that your bra may no longer be fitting you, thus requiring replacement.

"If your bra is loose at the tightest hook and eye option, then it’s time to replace. Similarly if your bra is tight on the loosest option then it is time to be refitted. Overtime your straps can stretch as well, again affecting the fit," she says.

"Also discolouration from washing is a big sign it’s time to replace your bra."

Ahem, excuse us. We've got an underwear drawer to sort out.