Just changed my plugs, still look decent. bought them from Amazon, NGK Iridium (OEM), $9.54 each.

 

those plugs don't look any different than the new ones in terms of electrode shape or gap..... they have plenty of life in them yet... J series seem to be very easy on plugs

 

I waited until my 100,000 mile service on my TSX and RDX for plug change. I've felt a slight bump in power on the butt dyno, improved throttle response, and slight increase in mpgs closer to EPA numbers after the new plug install on both vehicles. I just didn't notice the slight power and mpg loss over the years because it was so imperceptibly small over time. I did my spark plug change on my 11 MDX at 75K to make sure I'm close to max performance levels at all times for the big girl. I didn't notice the same improvements on the butt dyno; but, I expect I'm good spark plug and have consistence performance/mpg until +150,000 miles.

 

I changed mine because I just bought this car used and the mileage was up there already, so I wanted to get the most out of the engine in terms of performance and fuel economy for the next couple of year I will drive it. Changing the plugs was good anyway, engine runs smoother and the throttle response is much better now, and it only cost me $60.