[Elbo]

They are rated at greater than 3000 hours

So if you don't drive around with them on in the day time

If you average 15,000 miles a year on your Titan
and drove 5,000 of your miles at night,
at an average of 45 mph
You would use your bulbs 111 hours in a year.

At that rate they would last 27 years.

I think HID's dim gradually over time. So you probably want to bail
on them after about 15 years or so.

HID type bulbs are typically supposed to last between 500 and 5000 hours
but speciality type applications have the bulbs lasting 50,000 hours or five and
a half years!