Just to add my experience with H spa, I have used it several times in the past 20 years but I sent a Box and a Barenia bag a few months ago and after keeping them for 3 months (no, they didn't go to Paris!) they came back exactly as I left them!
Although I'm nowhere near as clever as some above ladies in restoring bags, I do treat them myself: Box with Saphir Restorateur or Nappa, and Barenia with Hermès Baume. So from now on, unless I have real damage on a bag, I won't be sending them into spa anymore.
Just an anecdote from about 10 years ago, I sent a Vache Naturelle Birkin to the spa (Paris) as I was scared to treat it myself. After at least 3 months my SM called me saying that my bag had come back but it was ruined
(Imagine Paris sending a ruined bag back as if everything was OK....) My SM , now retired unfortunately, told them straight out that they had ruined the bag so what would they do about it? Paris admitted the damage and made me a brand new VN bag in 4 months! By the way I never saw the damaged bag.