Depends on which hoya. Some like my multiflora/javanica like to stay moist. In contrast, I don't water my aff. waymaniae until it is almost completely dry. Hoyor has some good guidelines for watering different hoyas.

Here is a link that might be useful: hoyor

Yeah, it does depend on which hoya species / cultivar you are talking about, but also on the kind of soil it's in (how water retentive it is), on the pot size (small pots dry out faster), the pot material (unglazed clay breathes and so it dries out faster than plastic of glazed ceramic), whether the plant is root-bound (it'll soak the water faster if so), if it's sunny or windy or humid, how much leaf mass there is (more leaves = more evaporation) etc. etc. etc.

Answers like "once a week" are going to be useless if there is no context. Rules like "when the medium is approaching dryness" are much more helpful.

Why do you ask?

As often as needed around 8 pm

That's funny, NN! I'm more of an a.m. waterer myself!

If the medium feels dry to the touch, I water. This can mean anywhere from every couple days in the heat of summer to once a month in the dead of winter.

Denise in Omaha