So my 1992 AKG K240 headphones are not much longer for this world. They have served me well as my all purpose headies for many years - checking mixes/masters, studio tracking, headphone monitoring etc. I like their sound, although not perfect, it's a sound I have got used to for reference. Can anyone recommend a good monitoring/general purpose, good sounding reference headphone that will last me another 25 years and be as good if not better than these old cans? I'd prefer AKG, but I'm open to all suggestions. I use them for recording but even though they are open back and I monitor loud I never get problems with bleed that I can't cope with. As I do most of my monitoring through speakers, my headphones only get occasional use for monitoring, checking mixes, vocal tracking and late night manoeuvres!

35mm
So my 1992 AKG K240 ... it's a sound I have got used to for reference. Can anyone recommend a good monitoring/general purpose, good sounding reference headphone that will last me another 25 years and be as good if not better than these old cans?

I'd get another pair rather than try and learn another 25 years of familiarity on a new pair.
 
As far as headphones go (and studio monitors for that matter), I'm of the opinion that as long as they are "decent" then it's not how they sound, it's how you know what to do with that sound that matters most.
 

have the AKG K712 and cannot recommend it.
great detail and stereo image but too much high mids and too little low freq.
Sennheiser is a better choice, IN MY OPINION.
 

I really like the AKG-702. Serves me well and prices have dropped quite a bit since I bought it ...

BTW I also got a ~ 1990 AKG - it still works and I still like it.

Open backed, Beyerdynamic DT990Pro are what I'm using at the moment. Pretty flat sound put of the box, just a bit of bass end lift.

Closed back, and so more suitable for tracking to avoid overspill, Senheisser HD25s are reasonably priced and pretty good. Again, something of a bass boost though.

Both are covered by Sonarworks plugin profiles to flatten the response, which is a very useful plugin to have if you have phones that it covers. Waves NX now has a profile for the Beyers.

Though if the same phones that you're very used to are still available new and haven't been significantly changed over the years a straightforward like-for-like replacement might be the best way to go.

Thanks for the suggestions. My 240s do still work and I still use them, but they are old and battered. I will still keep and use them but need a new pair that can take over the workload and ideally be an improvement over the 240s. I could get a set of the new 240s for consistency, but even they are different from the old 240s. In any case, it won't take me long to get used to a new set. I was used to DT 100s before the 240s as they were everywhere so the 240s were a huge improvement at the time.
 
My problem is that I live out in the sticks so can't just go and try a load out. I'm hoping to find something that's an improvement over the 240s and that has a good, accurate sound. I always find closed backs boost the bass where as open backs can produce a more natural, open sound. I also want the over ear type. I guess it's subjective and people will recommend what they use, but if anyone has had a chance to compare different head phones, recommendations would be appreciated.

If I had a choice of headphones now. 
 
AKG K712 or 812 or 872
Audeze LCD
Sennheiser as well I suppose, however the benefits are gray area once you're at a certain price. You expect neutrality and balance when you spent so much on headphones. Since you probably want to hear the room as well I think open back as well.
 
Depends on your budget obviously however I would see what's on offer.