Well, regardless of the 2 week timeframe, I know plenty of cases where the other partner is abusive and only really started up once they were secure in the relationship, and then they eased it in, rather than just starting full tilt.

It's like that thing about the frog and hot water. If you drop a frog into hot water, they'll try and jump out. If you leave them in a container and slowly heat the water, they'll stay in there until they die.