My wife will borrow my phone quite often, as I usually have far more credit left at the end of the month than she has. We have unlimited time between each other but not to other numbers – she runs out. She has never read my texts to check up, but she will to see what our kids are up to – they will often only text one of us.
I don’t think that in any good relationship there should be an necessity for hiding things, but if suspicion is aroused, being able to alleviate it can only be a good thing. But, as mentioned before, phone checking is in way pointless, as it really can’t exonerate, it can only confirm. Anyone with sense will not leave incriminating messages on their phone.
Far more telling would be a close examination of the phone bill. You can’t delete the records of constant calls and texts to one number.