The verdigris will come back. About the only thing you can do is try to manage it. The Pecards in no way prevents it's growth, but does seem to make the new growth easier to remove.

As to whether is will corrode steel, I do not know. I have seen pistols that had been stored in holsters for years that showed no signs of corrosion from the verdigris itself, but would not recommend storing a pistol in a holster whether it had verdigris or not.