[RodKnock]

Look at some of my threads as well as many others here on CC. I started the DMV process one year ago, when I bought my car. I got my SB100 certificate on January 2, 2008. I just got my plates and finished the process last Friday. To the best of my knowledge, the certificate does not expire, but if the entire process takes a long time, like mine, then the DMV will send you an "Incomplete Registration Notice." It seems to me, if you just pay your taxes, fees and such, then you can go on indefinitely, but I wouldn't try it.

1. Start the process before January 2nd. Start the registration process and pay your fees and taxes. If you're building a new Cobra, you must have the original MSO from the manufacturer and any receipts for parts and labor, if you have any at this point. Otherwise estimate the build cost fairly. Always disclose that you car is an SPCNS car. Never ever say it's a 1965 Cobra or whatever. At the BAR appointment, much later down the road, you will tell them that you want it tested based on the year the car replicates, not the engine, but otherwise, your car is an SPCNS.
2. Get to the DMV early on January 2nd. Very early. Depending on your DMV, maybe the night before.
3. Go to a DMV in your area that has at least some experience with the process. The more experienced DMV, the better off you are.
4. Make sure your paperwork looks correct before you leave the DMV after every visit.

There's more, but that's the basics for January 2nd. Eventually, you will have to visit the CHP (VIN assignment) and then the BAR for the smog test and smog exempt sticker. Also, the DMV may or may not require a Brake & Light inspection. I got one.
Good luck. I may have forgotten some things, but those are the basics.