Is it better/worse or doesn't matter to have an "official" "fail emissions" when trying to renew registration? Will it buy me more time?? 1998 car. But runs well except odometer sometimes doesn't work.

That is hard to say exactly. That question is better suited to ask the DMV since they would be able to better suited to answering the question. As an Emissions Testing Center we mainly handle only doing the Emissions Test itself or repairs.

You cannot register with a failing test, unless you qualify for an exception. This involves spending $$$ on repairs in an attempt to pass the test and still failing. I'm not sure how much you have to spend to qualify for the exception.