I love vague terms like "long periods". Long compared to the Planck length? Geological time? Is the advertised 43 seconds almost there or "off by 17 orders of magnitude?"
“Off by 17 orders of magnitude” would be off by 136 billion years, so not that much for sure. Assuming you want to be able to test the plant and or maintain it once per year, 43 seconds is less than 6 orders of magnitude off. The jump was more than a full order of magnitude compared to past records, so another handful such developments and we are there.
Nuclear already gets taken offline for several weeks for refueling, but redundancy covers such issues.