Hoya merrillii is a prolific hoya. Once it started blooming the umbels will produce buds as soon as they are spent. Sometimes, there are even already young buds while other buds are still blooming. However, they don't form very nicely rounded umbels like the other hoyas in my collection. In fact, the first time they flowered they look so disorganized. But they produce a lot of umbels to compensate for the unharmonious patterns of the pedicels.
Here are two umbels arising from the same node. They are prolific aren't they? But look at the lenght and directions of the pedicels, unrully i tell you! They also have a mild scent that maybe very attractive to the moths and insects, but for me is not top of the line. That is because i have other hoyas with sweet scents that can be made into perfumes, if the nectars are just very plenty.