I have had a fireclay sink (Shaw's) for 6-7 months, and it looks as good as new. I use a sink grid in the bottom, to avoid scratches, I think that is important. But nothing stains it, and I have not had any scratches anywhere else yet.

I have a fireclay sink (Herbeau) since Christmas and it is holding up beautifully. I love it.

I've had a white Whitehaus fireclay sink for a year now, and it is as fresh and white as ever. We use the sink grid, but more to protect glassware when washing up than to protect the sink itself.
Like any other non-metal sink, it would likely chip if you swung a big ol' cast-iron griddle at it, but we use cast-iron pans all the time and nothing has transpired so far.

We can be complete slobs and dump everything in there and often leave it sitting: ketchup, espresso grinds, wine. Barkeeper's Friend cleans it spotlessly each time. :-)