So, I was curious about this also and looked it up. There was a thread in 2010-2011 that asked this and about 5 people reported chipping happening in 6 months or less, but the majority had personalization for years and nothings happened to the paint. Then again, this was over 10 years ago now, and with quality declining… who knows nowadays.
If it makes you feel any better, Angelus Direct has some really good purse protectors and paint sealants. I’ve used their paints and top coats on canvas pieces I’ve painted, I’d say the oldest is about 3 years old and there’s no signs of chipping, and I’m rough on bags. They’re a brand that specializes in shoe customizations, so their stuff is made with shoe wear and tear in mind. They also have aerosol cans for waterproofing and protecting. Haven’t used the aerosol on vachetta (my Mon Monogram will be my first piece with vachetta) - but I’ll make it a Guinea pig.
I know some people don’t like altering their bags or apply products in any way, shape, or form. However, if you do want a MTO piece and can’t find an answer, I can vouch that I’ve never had an issue with canvas I’ve personally painted.