Are photos deleted off of an iPhone always recoverable?

The reason I'm asking is because the other day a friend of mine asked if I still had photos from a particular evening about a year ago. I deleted the photos several months ago. Is there any way to access them? I saw somewhere that deleted files eventually get overwritten and cease to exist.

You can use the recoverable software. But carefully handling because your phone is expansive your memory open the phone and you can use card reader uses.