Ok, my friends from Japan told me the vachetta would crack if I kept the plastic on too long.
Thank you!
I would take the plastic off then keep the bag in its dustbag. Sometimes the vachetta starts to darken a little even though the bag is unused, and you'd really hate for the rest of your bag to be darker than the handles...
Oh well. I took it off and put it back in the dustbag!
You did the right thing Sophia. I think it's best to take the plastic off and store the bag in its' dustbag, otherwise the leather wouldn't be able to breathe properly through the plastic and, as someone already mentioned, it would patina more slowly than the rest of the bag...