Rather than stick with established technology, it sometimes pays to replace standard navigation lights with LED alternatives. They’re just as bright, if not brighter, with as little as 1.5 watts draw as opposed to 15, and if one element should go bust (10,000 hours life expectancy), you’ve two left to lighten your darkness. The cost is more (something less than double generally), but some existing lamps can be converted to use stand-alone bulbs. Ask anyone who’s had to crawl around the pulpit while sailing to windward on a dark night trying to change a bulb and he’ll tell you they’re cheap at the price.