AirPods losing significant volume I'm a heavy user of the AirPods 1st Generation, probably using them for 6–10 hours daily. Currently, my left AirPod has gradually, but also quite dramatically, lost its volume capacity over the course of a couple of weeks.
It would be vital for you to know, that this is not the first time this has happened. I have been an AirPods owner for about 1.5 years, but during that time this problem has occurred with both my Left and Right AirPods multiple times at different occasions. I have been able to get replacement units from Apple as the decreases in volume has been significant. I believe my current Left AirPod is the fourth unit I've owned which exhibits this problem.
I need to pan the audio in the system to achieve a rough L–R equilibrium. Currently, I need to pan the volume 50% Left from the Middle, which indicates a 50% volume loss.
While the deterioration has been slightly gradual, it may also occur dramatically and suddenly. In fact, two times (with different units) the volume capacity has gone jumped from unnoticeable to about 20% loss and then almost 50% loss over the course of a week or two. This would suggest to me that it's not due to earwax buildup, but something technical, but I'm not sure.
I have tried the AirPods on multiple systems, so I know it's something relating to the unit and not the OS. I have tried cleaning them quite routinely, even by following this suggestion to suck on it to remove potentially clogging earwax from the behind the membrane. Unfortunately it doesn't seem to help.
Does anyone know what the problem can be, and how to fix it? If it's likely due to dirt, is there a sure-fire effective way to clean them? For equipment at this price, it doesn't feel satisfactory that they lose significant volume over time.

Update regarding AirPods Pro: I now own the AirPods 1st Generation, and also since six months back the AirPods Pro. The problem of suddenly and significantly losing volume – as described above – has been delimited to only the 1st Generation AirPods so far, and this has happened at least with 3–4 pairs of these 1st Generation AirPods that I have replaced thanks to the multi-year consumer protection laws in my country. They have failed every six months or so.
The AirPods Pro have not exhibited the problem of suddenly losing significant volume, after six months of usage. Apple may have resolved the issue, but it remains to be seen. However, the AirPods Pro does lose volume gradually due to continual use, despite cleaning. Max volume is perhaps 20–30% less than upon purchase. I would recommend people to replace their AirPods after the damage becomes significant enough, because I view gradual loss of volume as a product failure.
If you are close to an Apple store, I would take them in for a factory reset / genius bar. See if they have any suggestions on monitoring. Unless you could use an otoscope or camera to show the ports clogged with ear wax - the total sound pressure can't be affected by some minor amount of cruft.

Also - in that setting you can close your eyes and have the tehnician move the balance and you can tell them when to stop the pan. If you're accurately hearing the sound output, it should be clear to everyone that you're carefully calibrated your ears and you are getting a different stereo mix when you use the same iPhone with wired headset and AirPods.

At that point, I would expect them to offer a full reset procedure and then a replacement set to be sure yours are not defective. At that point, once they are sure you're not getting proper volume, they might want to do an engineering capture / get you brand new set and/or refund your money.

I don't doubt you're getting poor volume and if you can get the support staff on your side - they might even fix the bug for us all. Sorry it's on you to prove it's hardware - but I had to go in to learn the reset procedure and a factory reset on AirPods was something you want on the service record if you want to get a paid swap / refund since it did solve volume and sound quality issues for me on one pair of AirPods.

Since I do live close to stores, I wouldn't do any cleaning other than what Apple says - and I request staff to instruct me how to clean it - possibly pointing out the cleaning KB and I'll review with them what force is safe from canned air, vacuum, etc... I wouldn't even go down the path of "suck on it” since the force from the suction could probably unhinge / break many headphone speakers unless they were internally vented in a very clever manner. (AirPods may in fact be, but I'm sticking with Apple on how to clean / maintain these.)