Using just one wireless earbud can be convenient for calls, translations or staying aware of nearby sounds, but regularly favoring the same side may cause the two earbuds to age at different rates.
The earbud used most often goes through more charging cycles and generally consumes more power, particularly during phone calls and Bluetooth transmission. Although both earbuds charge in the same case, the frequently used unit may repeatedly reach a lower battery level and require more frequent recharging. Removing one earbud from the case more often can also contribute to uneven charging patterns.
Over time, this imbalance can leave one earbud running out of power before the other. With some older or lower-cost models that use a master-and-secondary connection arrangement, the result may be even more restrictive: if the primary earbud runs out of battery, listening may not be possible at all in mono mode.
Many newer wireless earbuds support mono playback from either side through role-swapping designs. Models such as Samsung Galaxy Buds and Google Pixel Buds are cited as examples. Alternating earbuds can help distribute battery cycles and wear more evenly when using only one is unavoidable.
The simplest way to avoid the problem is to limit single-earbud use to occasional situations. If the goal is to hear the surrounding environment while wearing both earbuds, transparency or ambient modes can provide an alternative by allowing outside sounds through. Some earbuds can also activate this mode when they detect voices.
For private calls in a vehicle, using a phone's speakerphone feature, Apple CarPlay or Android Auto may be preferable to regularly wearing one earbud. Dedicated single-ear Bluetooth headsets from brands such as Poly and BlueParrott are another option, although they are mainly intended for professional use and are larger than modern wireless earbuds.
Sources: Engadget.