Every time it's happened, the first thing I do is switch the ballasts to ascertain if the issue is the bulb or the ballast. It's always been the bulb. When I've installed them in the past, I put the rubber boot on behind the headlight. Methinks that there isn't enough air circulating, which causes overheating. ..which is why the brights still work, as they haven't been overheated. At least that's my theory. This time I didn't use the boot, but that causes condensation to build up in the headlight. Like I said, when these go out, I'm going to switch to bi-xenons....no fan/airflow issues. If they don't suffer in the Hellas, they should be fine in the headlight assembly.