Derfred,
Agree to disagree.
I set the cruise(yes the highest) given on the flight plan,be it if any intermediate level offs.
For example, if you have planned to cruise at FL370 (that is your top of climb - perhaps your flight plan suggests a step climb to FL390 in 3 hours' time - that is irrelevant), you would have FL370 set in the FMC and the pressurization panel. If ATC clear you to FL310, and advise to expect to be cleared higher soon after passing under crossing traffic, then FL310 is not your final cruise altitude so you would not set that in the pressurization panel. You would leave it at FL370. After a few minutes at FL310, ATC tell you to climb to FL350, FL370 will not be available due traffic. Now FL350 has become your final cruise altitude, so you would set that in both the FMC cruise page and also the pressurization panel.
How to make easy complicated...I wouldnt,better things to do.
Again,an off schedule descent,if it occurs is a non event.(even if yes technically you need to read a single line in the qrh),however a flight above your "multiple reset" altitude is an event and possible incident if it goes as far as triggering the pressure relief valve.