I just learned I've had my pair of DT770 Pro 250 ohm for 7 years to the month as of writing this. I don't recall lower impedance models being available at the time, so I've always paired this with a good amp where possible (these seem to wear out fast for some reason). Right now I have them plugged into a USB powered DAC, which is probably a little underpowered, but seems fine otherwise. Basically, these are my go to cans while working, and my longest lasting pair of high quality headphones. I've had other people listen to them and find their audio reproduction and sound stage to be great, especially for the price. I use to be a Sennheiser guy until I got these, and I haven't found a pair of headphones in this price range be comparable.
And that includes today, on a 7 year old pair of headphones.
So I can give a good long term view of them.
I've replaced the pads once since getting them. You can find replacements pretty easily. I let the originals go way too long, to be honest, as they came apart as I took them off. But putting on the new ones was no problem, and it completely renewed the feel. I probably should replace them a bit more frequently, though. I'd consider this a consumable wear item.
The plastic bits with L and R have cracked, but it doesn't seem to impact their fit at all. Plastic gets brittle over time, and after 7 years of abuse, they're still holding together just fine.
The wiring seems to be holding up quite well. No issues with stress or anything. The coiled wire has stretched a little at the ends of the coiling from the weight of the cable over time, but there's no concerning issues there.
If you listen to highly compressed audio, you will notice with these headphones.