“work wife” or “work husband”

being in a relationship, how do you feel about the terms work wife/husband (if you’re not familiar basically it would be your coworker who you work all of or a lot of shifts with, spend a lot of time with, really close at work). do you feel it’s disrespectful to the actual husband/wife or boyfriend/girlfriend? even if you weren’t/aren’t in a relationship, should the terms husband & wife be saved only for actual marriage even if it’s a joke??