Depends on the relationship IMO.... with my wife after 4 months (of dating, not marriage!) we were still learning new things about each other, it would have been too soon. Whereas I probably could have tried living with my ex after a couple of months, had circumstances allowed, she lived life at a much faster pace and I probably knew everything there was to know by then.
Wife and I bought a house together after about 15 months, in hindsight it was probably a mistake and we'd have been better off renting, but we were really keen to live together and could afford to buy so it seemed like a good idea at the time.
Practical matters apply too, i.e. how difficult do you find it living apart? Is there a lot of travelling involved? How much of a financial strain will it put on you?
Wife and I bought a house together after about 15 months, in hindsight it was probably a mistake and we'd have been better off renting, but we were really keen to live together and could afford to buy so it seemed like a good idea at the time.
Practical matters apply too, i.e. how difficult do you find it living apart? Is there a lot of travelling involved? How much of a financial strain will it put on you?