It's only vile when you project insecurities or bad intent...
We both know each other's passwords for everything. We use a shared database for it. We both know each other's phone, unlock codes and often through laziness will just use each other's phones for shit. We shared the same bank accounts, we don't have separate money. We share the same vehicles....etc
What's mine is hers, what's hers is mine. Except literally.
We also both have each other's location. What do we use this for? Essentially nothing except when one of us is traveling, or someone is feeling neurotic/worried. The peace of mind knowing that your significant other didn't just die in a car crash part way to their destination and are still making progress is significant.
We don't hide things from each other, we've explicitly built a relationship of openness and trust, brought on by us actually_not_ trusting each other for a long time. We are completely transparent, and you know what this has helped build? Trust. Know what it has torn down? Insecurities. It's been great.
Would recommend.