How long is it normal to be seeing someone before moving in together?

That is, what would surprise you least?

I know this will prompt a long long discussion about stereotypes, how there's no such thing as 'normal', and how you can't generalize, etc. etc., but I'm genuinely interested to find out what people think about this.

And I'm actually wondering more about how you see your friends and acquaintances than your own standards. (e.g. I'm not remotely the moving-in type myself, but that doesn't stop me being slightly amazed when a couple have been together for 6 years and are still living apart, and worried/sceptical when friends move in together after dating for less than a month.)

My advice is always to give it at least a year before moving in together. And I almost always have ignored this very advice to my own detriment. On the other hand, my wife and I waited about two years before moving in together (we obviously weren't married at the time) and we're still together.