It takes me a long time to warm up to the point where I'm ready to masturbate - I've got a pretty low libido and I'm easily distracted. Usually I'm only interested if I've just spent the last hour or two reading erotic fanfic >.> <.<
Once I'm ready, though, it only takes me about five minutes I'd guess. I'll usually keep going for one or two 'aftershocks' but all in all I'm in, out, and exhausted in fifteen minutes max.
Oh, and I use both hands, my dominant hand for control and my off-hand on top of that for added pressure. I have NO idea how long it'd take me with just one hand, I really like having something pressing into my whole crotch, not just working the clit or canal. I ish weird o.o