No matter how well you think you know your significant other, there are plenty of things you probably won't discover about them until you share a roof together. Everyone has weird quirks and idiosyncratic behaviors that they hide from everyone, until they no longer can. Because they have nowhere to hide. This is why co-habitation can take intimacy to new levels—and also push relationships to the limit (and sometimes past their breaking point).
Someone asked cohabitants of Reddit: "What's something strange that you discovered about your significant other after moving in together?"
My husband is deaf (to clarify, I did know this before we moved in together).
The thing is, I had NO IDEA how loud he could be. It should have occurred to me sooner, but he has no concept of his own volume. Listening to him make a cup of tea is like having the cast of Stomp in our kitchen.