Hello Richard, PoolMike, others -
We drive (and camp in) our Sprinter year round. Our home base is in the Boston, MA area where we get everything from hot and humid to plenty cold. During some parts of the year we will get a fairly broad range between high temperature and low temperature during a 24 hour period.
We have driven our Sprinter up and down the East Coast (Canada to the Florida Keys) but we have yet to take it into desert areas. Are the folks who are encountering bulb failures located in desert climates? Maybe the heat of the sun during the day followed by the sometimes very dramatic shift to cold temperatures at night is playing a role here?