I received my first Hoya flagellata plant around four years ago, and it took about 18 months for me to finally kill it.  Before it died, it managed to put on a peduncle but never budded up.  Last April I ordered another cutting in a Thai order and it rooted but has not grown even one leaf in that time.  I could not tell if it was alive, or dead.  I guess it was still alive as about a month ago it grew a thread like peduncle, and this time it did but up.  Here are a couple of photos of the entire miserable looking plant: