Does this spark seem to have been used for less than 8,000km?

My mechanic has charged me for sparks replacement without asking me, telling me they needed replacement. That happened a few months ago. Now, I took them out and this is how they look.

So, what is most reasonable? are they the ones I replaced 2,5 years ago, or could they be 5-6 months old?

From my limited understanding, I would say they are quite old and dead but I need to confirm.