My friend is a senior in college and has been dating her boyfriend for seven months. They're planning to move in together, but I think it's too soon. How long do you think couples should date before moving in? What should I say to my friend?
If this is a short-term situation to get your friend and her boyfriend through the summer after graduation, then that's a reasonable post-college plan. When it comes to couples cohabiting without a specific end date, it's less about how long they've been together than whether or not they have plans to make a permanent commitment to each other. While it's possible that a senior in college is thinking in those terms, it's more likely that this arrangement seems like a fun way to save on rent and play house.
If, as I suspect, your friend is planning this move without any specific commitment between her and her boyfriend and without a backup plan, she would do well to reconsider. I want to emphasize that this advice is based more on the commitment aspect than on her age or length of relationship. If a couple of 30-year-olds have been dating for four years and decide to move in without specific talk of the future, that's just as problematic as what you're describing. (Actually, probably much more so.)
Still, I think you should keep your concerns to yourself. Living with someone and then breaking up causes total havoc for both parties, but the year after graduating from college is pretty much havoc anyway. If her heart is set on moving in with him, your attempts at dissuasion are more likely to make things awkward between the two of you than to change her mind. If she shows signs of doubt, though, and comes to you for support, that opens the door for you to ask guiding questions that might lead her to realize this isn't the most perfect plan. If she goes ahead with it and things go wrong, please, please try to avoid any form of saying, "I told you so."
I recognize the frustration inherent in being told, "You're right, but don't do anything about it." Still, I hope you'll be able to let your friend find her own way in the coming months. Regardless of her living arrangements, she'll need your friendship as she goes through all kinds of transitions in the coming year. The more non-judgmental support you can offer, the better for both of you.