I think needy people do it quickly.
Independent people will give it quite some time,they don't want to have 'their' freedom compromised.
I would not advise it.....but that is just how I see things.It can have a nasty outcome in a few months, and then that has a way of keeping you from trusting.
I think if it really is on the cards, then at least know the person for 6-7 months before even going down that road.
Freedom is such a liberating experience, and it is not always going to be there!
Enjoy life....do what you want, without having to answer to a partner.
You have to be o.k. in your own company, before you can consider living I believe, with some one else.
If I had a chance to live alone, just for 6-12 months I would.
Once you move in together, it's all about consideration of each other.
Sounds fun?
In reality, it is a LOT of hard work, and believe me issues come up from time to time.
As for finding out about that person, before marriage I guess is something people feel they need to do.
A longer engagement will fix that, once you have committed, it is very hard to walk away.