Why do two of three bulbs burn out in my light fixtures?
I may not agree with others but many times it is the connection to the lamp that is the problem. The center conductor getting folded down a little more than the others and the lamp arcs until it no longer makes a connection.
I would try (with the power off) to lift the center tab a little. These tabs are many times brass and they do have some spring to them.
A kitchen knife to lift it up a little like 1/4” so it makes a solid connection may be the fix you need to have lamps that last closer to the same life time.