We have a number of inexpensive light fixtures in our house, each of which takes two bulbs. Most, but not all of these, are on newer dimmer switches (two with sliders, one with remote). We're having a consistent problem where one (but only one) of the bulbs in each of at least 4 different fixtures fails every 1 to 4 months. The other bulb will continue working, at least for the 2 years since we installed them.
Since LED bulbs are supposed to last for 5-10 years, and are difficult to dispose of, this bulb burnout is kind of a problem. So we're looking for advice on what is most likely to be the problem, and what I need to fix/replace to stop burning out bulbs.
Here's what the bulbs & fixtures have in common:
Here's what they don't have in common:
So, ideas/suggestions? What is the most likely cause of this one-of-two bulb burnout, and what's the first thing to try replacing?