VNTM:How long can you keep your underwear?

I was doing laundry the other day and I was de-tangling my unmentionables and I rendered up the inquiry as in to how long I've had some of these garments and if it's time for me to renew my drawer with new ass garments...how long is it OK for you to keep your underwear???

I've been having these underwear for almost 3 years.
This was a unregistered question.I rarely purchase underwear for myself (Grandma takes care of that around Christmas and a occasional date or two may cop me a few sexy pair every now & then...) and the one's that I do have in inventory I love and don't feel the need to dispose of.

 
I researched and came up with this solution....
The only exception to throwing out your favorite underwear are :  

• If they start to rip.
• If you can't get those embarrassing shit stains out.
• If they become faded .
• If the elastic starts to ripple and threads unravel: (your ass getting too big Precious!) 
• If that label on the elastic band (i.e Calvin Klien,Diesel)is no longer visible.Can it!

Now if you don't have these complications then you are good on your pieces.