[Shaffer]

Sony V6 purchased about 6 years ago. Admittedly, I use them very rarely.

In terms of heavy rotation, as in almost daily use, it would be ~3 year old DT990pro.

 

[Madscientist970]

Koss Pro 4AA - I rarely play them. They are are such an iconic headphone though! 

 

[Nelson Soong]

Been faithfully sticking to my ATH M50s for the past 3 years. No intention to change yet because it is awesome. =)

 

[alpha80]

I've had Sony MDR-7506's since 2003.  Still performing perfectly, been thru three sets of pads though.
Enjoying AKG K701's since 2005.  Likewise, but with zero replacements at all, under 5 days a week of heavy use.

 

[critofur]

AKG K340
 
At least 20 years old?
 
 

 
I also have some little red foam pad AIWA "walk man" type headphones from around 1984, and some cheap JVC full size headphones from ~ 1990.
 
I mostly use my ATH-M50 but just ordered a pair of Sony 7506 so I can have some with less bass exaggeration for when I play FPS games.

 

[nordkapp]

HD 580s. 2003, original owner. Tried and true.

 

[bozebuttons]

Grado SR60 that came with mini flats bought new in 1995 ,picked up a Rs1 with wooden box 2months later still have them.

 

[jnorris]

Sennheiser HD400 from the year Q, Audio-Technica ATH-7 Electret from the year R.