Utterly depends on my mood. My So is amazed that I, as a girl, can take a shower in two minutes. On the other hand, if my mind is preoccupied (feeling blue, trying to figure something out, etc), I lose track of time and the water will put me into a trance. Also, I have long hair down to my hips. It takes some time to take care of that
Then half an hour is no problem.
Probably about 15 minutes. It's one of those things where the near-OCD tendencies start appearing. (Not clinical or anything...just tendencies that would be OCD when taken to the extreme.) The way my hair is run through has to feel just right, and until then, it won't be satisfactory. Hard to explain. Keep doing it until it "feels right". That's the same way I pick food when I go out to eat, keep looking until I see something that just looks like it would "taste right" for what I'm hungry for.
But also part of going rather slowly through the shower for me is that I do kind of zone out and forget what I'm doing, but not for long.
I like to take what I call "shower-baths" (basically showers in a combination shower/bathtub with the drain plugged so that the tub gradually fills up) untill the hot water runs out. Unfortunately, circumstances make that impossible right now.