I'd say add a fan to exchange the air the cabinet and promote better cooling of the ballasts. If the air in the cabinet isn't exchanged it will heat up from the ballasts and reduce the temperature difference causing the ballasts to run hotter. This will happen even if there is lots of space in the cabinet, it'll just take longer to heat up. There's not much else I can think off that cause premature failure although I would have thought the electronic ballasts would be less of an issue...
|