The Nissan Path

Should the power steering fluid on my R51 need changing at some point or is it not ever required?

Nissan only says "inspect" every 15000 miles. If it looks dirty, you could flush it. Just don't use clear or amber Power Steering fluid. Stick with automatic transmission fluid, like Dexron III or Nissanmatic "D," or genuine Nissan power steering fluid. You can also use synthetic ATF, like Valvoline Maxlife ATF.