Hoya macgillivrayi flowers at least four times a year for me and it is only the grow tent and artificial lighting that makes it possible. I have a huge six year old specimen in my living room that never flowers and will never flower because of the lack of enough 12-14 hour (day length) days. If you really want to flower your Mac, in the north where I live, you have to grow it using lights. Here is a photo of some very fresh buds from this week: