It probably doesnt take long to do it, but its the maintaining it that I would imagine is the problem. A few grey hairs never look bad on a guy, whatever the age.
Not that this is in the least bit relevant, but its kind of odd how I (and probably lots of us) are very passionately in favour of having a hair free head, yet I (and lots of us) would rather die than have a hair free face 
You couldnt offer me enough money to have a naked face.
I've been coping a bit of flack recently over my beard, it tends to happen from time to time. It's got to the point were some people have queried if I'd shave it off for money. I've set the price at $1000 to go clean shaven, no one has accepted the offer. People scoff until I explain the time and money invested in growing it to this length.
Would I actually shave it if I was presented with that money... I honestly couldn't say, but I know it would still take some arm twisting.
The one time since I was about 19 that I have shaved my beard was when I was forced too for work, they quoted it was in the rules, but wouldn't show me where it was. I fought them on it for months, but one day I was sent home from work before my shift started, and at the time I was young, and needed the money to get to uni, and really it came to the point it didn't feel worth losing ym job over. So I shaved it off. That day I told them once they saw me clean shaven that I was utterly embarrassed and we were going to have to come to some kind of agreement, on and there was the part about me being totally furious and refused to talk to anyone for the rest of my shift (was sent home to shave then return to work).
Now that I look back on it, I probably really should have done them from discrimination or work place bullying, something like that, and made a packet off them. But as a 23-24yo university student, I personally didn't have that kind of money.
Anyways, the agreement we came to is that I could grow my facial hair however I wanted as long as I supplied my own beard net, and that it didn't interfere with my work. So I refused to work any more customer service shifts, and stayed in the kitchen.