Spark plug wear

Hi all, I have a 2013 Jimny with only 27k miles on the clock. Although it's low mileage, the service history is patchy, so I've been giving it a long overdue service. Had the plugs out today, all look OK apart from a deposit on the ground electrodes opposite the centre electrodes. Is that normal for iridium plugs? Have these got some more miles left in them, or should I be sticking some new ones in there? I would assume these are the original plugs.

The plugs look okay to me, nothing amiss. There is some burn marks on the insulator which might be just age or could indicate running a little hot, but could also indicate a leak or wear on the integrity of the plugs.

There are similar to the plugs I took out of my 2011 with 65k miles, I cleaned them, checked the gap and put them back in, my Jimny ran better, but I checked the price on replacements and they weren’t expensive so went for a new set about 2 weeks later. The old plugs I had cleaned came out good aswhen they went back in, so there was probably nothing wrong wit hem once cleaned.

Thanks both, much appreciated!

Just checked my notes and my plugs have been in since I bought the car brand new in 2013. Just approaching 70,000 miles