To only wash will take from 1.5 (Volvo beater) to 2.5 (WRX daily driver) to a minimum of 3.5 (S8)- depends how gentle of handling the car requires. But then, I ALWAYS do the door jambs, under the hood, wheelwells, etc. I wash as quickly as I can, as in aerobically demanding (and I'm in shape). It still seems to take me a long time.
When I do my friend's A6 (was my late father's car), it usually takes me an entire weekend, and I feel I give it a sorta sloppy job (at least compared to my cars).
To really DETAIL a car always takes me several days. I washed the XJS Friday (just dust from sitting all winter, still took 2.5 hours), compounded and coarse polished it Saturday (over 8 hours), final-polished it Sunday (over 10 hours, just doing the inaccessible areas with q-tips took forever), and I'll get some VM on it today. It won't be ready to drive until at least the end of the week. And then there's the interior to start on. Many, many hours, and that's working as fast as I can without getting sloppy.
I marvel at how some of you can do a whole car in a few hours, let alone you folks who do it without machines.
Cleaning the S8 takes so long I find I seldom drive it, which is screwy. I keep taking the Volvo because "it's already dirty" and it sits outside anyhow. I've been thinking I need to reprioritize this stuff, but after 18 years the XJS only looks like it does because I've spent more time detailing it than driving it.