Yeah, but maybe constant nose picking is a habit, yet they refrain from doing it in front of you and when sleeping over. But by living with them and when people become more relaxed and comfortable enough to be themselves totally, you would sharp cotton onto this unpleasant habit and it could be 'offputting'. Say you married them and before knowing this....then I guess you are stuck with a nose picker.
My friend married a guy who peed the bed often - if she'd lived with him beforehand, she'd have known this was what she was marrying.
I think there are still some things you can't know and until you live together. I discovered shit about my ex H after marrying, that I didn't know beforehand...like he was an avid porn watcher who would hide porn movies all around out home. Not that it bothered me, but it would have bothered some women. I think I would live with a guy and before marrying....try before I buy, so to speak lol