I thought it likely this would turn into what one ought to do - and I can't disagree with the good airmanship responses posted subsequently. I think my second question sounded alarm bells and was poorly phrased.
Maybe the question should have been phrased: does an MECIR renewal also renew the PIFR(SE)? That's it, just what the rules say is what I was having difficulty finding.
What you do with your legally valid ratings is another (but not far removed) subject.