V6 Engine - Spark Plugs

Hello - I have a 2010 Murano V6 and besides mechanical wear and tear, it's run great. Now it has 230K miles, with many systems refreshed and ready for more. The only component I have not had issues with is the engine. Thankfully. I have used blend synthetic oil and faithfully changed it. I have owned it 9 years, put 150k miles on it and have not changed spark plugs. Does anyone have advice on when / if to change the plugs? Proactively just do it or wait for an indication? My fear is if a plug goes out, the other cylinder torque goes up by 17% to carry the load - and it is not a young engine.
Thanks.

I'm surprised your engine runs as well as it does with such high-mileaged plugs. NGK Laser Iridium plugs are said to be good for about 100K, whereas basic plugs usually start showing signs of problems much earlier. But a lot can depend on the octane of fuel you're using and other maintenance practices that may affect a plug's longevity. I used NGK Laser Iridums in my 2003 since around 120,000 miles, and they were very reliable.

I had planned to replace the plugs in my 2021 at 100,000, but recently started to rethink that since the engine runs so beautfiully. However, I've again changed my mind and will be installing either Ruthenium or Laser Iridium plugs within the next 5,000 miles. I figure by the time I detect a problem with the engine's performance the combustion chambers and valves are likely to already be suffering from increased carbon deposits due to a weaker spark, and once those deposits are there the damage is done. And let's not forget about the expensive exhaust system and sensors being more carbonized by weaker spark plugs. Better to perform maintenance at a reasonable interval before things get to the point of causing problems. In addition, the longer those plug tips are subjected to their explosive environment, the weaker and more brittle the affected components might become to the point that something could break off, fall into the head and cause major problems.

If you're saying your plugs have at least 150,000 miles on them, I'd change them out as soon as possible, along with at least the three ignition coils on the firewall-side bank, since they've likely already exceeded their life expectancy and since replacing them later will be more work than doing them while doing the plugs. The grille-side coils take only a few minutes to replace.

The other thing to consider is mileage, time and heat on those parts. The longer those "overdue" parts remain in use, the harder it may be to remove them because they'll really be baked on. You might snap off a plug inside the head or break an ignition stem trying to pull it off the plug, etc. There are many benefits to doing routine maintenance before things possibly start going bad or failing, and usually the only consequences are the time and money it takes to do that maintenance.

EDIT: And congrats on reaching 230,000 miles. I hope it keeps going and going...

Thanks for the insight. Agree. Any idea on cost to replace 2010 Murano plugs? Saw a video of it and the back 3 plugs look more difficult.