I usually just have the parts, I don't have room, or want the responsibility of storing someones bike. It can make things a bit tricky if you are doing a design which goes across two panels, when the parts aren't on the bike though. You need to make sure you mark out where the seat lights etc go as that can affect the design, and also which way up parts go, which is not always as easy as you might think sometimes. Some sports bikes have all sorts of weird shaped panels, and you need to know how they sit, so that you can make sure you paint them the right way round/or make sure the design is horizontal /at the right angle. How long depends on the state of the parts, is it ready to paint? Does it need rubbing down? Are there any dents to fill? Does it need to be stripped back for any reason. Will you have to do the primer, undercoat and basecoat too? Prep can take a long time. Does the client already have a design? If they do you will probably still have to tweak it to get it to fit, if not, and you will be researching, and coming up with an original design, you need to factor that in. Sometimes I can come up with a design fairly quickly, but sometimes it might take a few days. Also it depends how complicated or detailed the design you're going to paint is. It could take a couple of hours, or a few weeks. Then if you are clear coating it, you have to allow time for that too. Sorry I can't give a better answer, but there's a lot of things to consider that can affect timescale.