Mmmm like I said I don't do this type of art so I am probably not the best person to ask. I say as long as you keep the customer informed and offer refunds if you aren't going to be able to work for an extended time then you are fine. Most customers I work with are happy to wait as long as they see updates and progress.

HMMMM I really don't know. What I've seen before is that the customer can send the item back for repairs if they don't do anything to it themselves or put it through excessive stress. So if they wear it the first time and a sleeve falls off, it can be fixed for free, but if they were trying to alter it themselves or going dirtbiking in it or something it voids the warranty. There should definitely be some kind of deadline though, you wouldn't want to be repairing things that people have had and worn for years. You probably know better than anyone how long your own work should hold up for before normal wear and tear sets in.