yes, it could take up to 21 days to get your ip pin by mail. But, however, you could retrieve your IP PIN online at the IRS's Get an IP PIN site.
I created an account just to answer you alls question ( thank me later). Anyways, I was wondering the same thing after I'd requested mine. To answer your question- no, it doesn't take a full 21 days. Got mine in a week and a half. Good luck!