We are making ours using only fresh picked, de-stemmed elderblossoms and macerating them for six to eight weeks. The dried just doesn't have the floral nose and the flavor is not the same. Also, the dried won't include a significant amount of pollen, which is important to the flavor profile.
We are planting more elderberry plants this spring for future production. They don't take many years to mature to flower/fruit bearing. We only collect part of the plants blossoms and allow the rest to fruit. We use the elderberries to make Elderberry Flavored Vodka (w/o sugar). It's classified as a "Flavored Vodka" despite being naturally infused with whole fruit, and has no added flavors of any kind.
It's a trade-off on the bushes... every elderblossom cluster you pick is that much less elderberry fruit you will be able to harvest.