I don't really know much about Dacor, but in general, here are some of the parts that I would think about:

1. any type of igniter. They tend to all eventually get damaged. This is more a problem with glow igniters (which you wouldn't have on a dual fuel range), but even spark igniters can eventually die.
2. heating coils (e.g. broiler element and hidden heating coils under the oven floor).
3. any light bulb.
4. any part that moves mechanically (e.g. oven door hinges, any type of slides)
5. any part that could corrode. For instance, if you live close to the ocean, the venturi tubes are likely to eventually rust. If you live in the dessert, this might be a non-issue.
6. any electronic parts.
7. any plastic parts that could get brittle over time.
8. oven liners, in particular the oven floor, if it is replaceable.

Some of these parts could very well be industry standard parts. If so, you wouldn't need to stock up on them. Others are going to be specific to Dacor. You could stock up on all of these. But that's going to set you back thousands of dollars. That doesn't sound cost effective, either.

On the other hand, once you have all these parts, you could slowly sell them again on EBay. So, maybe, you'd recoup a little bit of your money...

Hello. I used to work for Dacor a couple of years ago. Although I never did to work on the 60" ranges, I would see them from time to time being built on the factory. Anyways, a good thing to have would be the parts catalog for your range. Here's a pdf version of it. Now keep in mind, you won't ever be able to change major parts, like the base of the unit, or the porcelain oven cell. But it does have all the part numbers of the components your unit uses. One thing I would definitely get are the relay boards (p/n 92028). Your unit should have two. They are the brains of your unit and with out them your ovens will be useless. Same with the control panel membrane (p/n 62309) that you can enter and set your oven modes. It too should have another controller (p/n 62790) behind it that will communicate with the relay boards. Convection element (p/n 82377), bake (p/n 62628) elements you should also get. Spark module box (p/n 86526) as well and the ignitors (p/n 76482-001). Also anything in the cooktop area that you can get. As far as sheetmetal parts, like the bullnose or side trims, I doubt you'll be able to get them anymore. So if you dent or do a hard scratch, that's it. Oh, don't forget to knobs (p/n 62021B). Anyways, like I said, take a look at the parts catalog, or rather download it.