Can I replace the Apple deal Airpods with another Apple accessory?

Well the straight answer for this is No. You can't replace AirPods with some other Apple accessory. But you can replace AirPods with new ones but you've to pay a little for them as well. If your AirPods are less than a year old and the battery is not performing up to promised 5hrs of listening time, Apple store will replace them at no cost. If your AirPods are out of warranty, Apple will replace them for $49 per stick, $98 total.

How much should AirPods last?

It actually depends on how often you use it and take care of your AirPods. Apple products are known to last longer than any other companies devices. AirPods should last you at least two years. With the passage of time their battery will stop charging as effectively.

But if you lost  your one AirPod or your Charging case, you can purchase a replacement. If you're looking for a single replacement AirPod, it's going to cost you $69. A replacement charging case will also cost you $69.