Flickering is a sign that they are about to fail. From experimenting with different LED bulbs, I've noticed the ones with fewer elements last longer than those with more. My single element 194 LED bulbs have yet to fail whilst I've already gone through several sets of 9-element, 44mm, 39mm festoons and 5-element 194 bulbs. I think heat is the culprit for those failures. I like the 'Super Star' LEDs because they come as either one or two incredibly bright LEDs per fixture and they have a nice metal case which acts as a heat dissipator.