There isnt an easy answer to this.

I think snooping is an invasion of privacy. However, i also think partners should have nothing to hide from their partners. Sometimes snooping is the only way to know if someone is cheating. If i never snooped i would still be with my pathological lying, psychopathic ex.

I have looked through my partners phone with his consent. I have major trust issues (Re: psychotic ex) and he was ok with it. I have also snooped without his consent. I do not have regrets because now, after 3 years of irregular random snooping, I know he is not a psycho or lier. I have talked to him about this. I have apologized and have stopped snooping out of respect to him. I really appreciate the conversations we have had as a result of this. I feel it helped both of us heal some past trust issues.

Snooping can easily get controlling and disrespectful. Trust needs to be a constant work in progress in romantic relationships. If you need to keep snooping you are basically telling your partner that you dont trust them. This is not good for the relationship.