They only draw atten-tion away from the text. During last year's interminable election coverage, I noticed a lot of waving flag backgrounds on lower-thirds. I would estimate that such animation is distracting enough to cause the viewer to spend approximately 20 percent more time figuring out what the graphic says. That's time spent not absorbing the program's primary content. With lower-third timings, don't take the easy way out.
Many editors use a set duration of five or six seconds for lower-thirds.
Although it's easy to program in the NLE, it's not as effective as the old trick of reading the title aloud twice and fading it off. Also show care about where in the sound bite the ID comes up. When time allows, let the speaker reach his or her first natural pause and then fade it on. This lets the viewer absorb the speaker in his or her surroundings before having to process the additional information of the speaker's name and affiliation. But unless your whole audience plans on gathering around that studio monitor to watch the program, adhere to the standards.