Do I need replace spark plugs?

Spark plugs are due at 120,000 miles. If he's going to be accessing that area for something else, there's no harm in changing them a little early. But I wouldn't do it early just for the fun of it.

 

He wants the $$$$ now. He doesn't want to wait 6k miles/6months more.

Just get it done at 120K or a little later.

For peace of mind, look at the pictures of my post when the plugs were changed at 120,631miles.
Spark Plug pictures after 120,631 miles | PriusChat

In the USA, CARB emission States say to change the same plug at 150k miles. Technically, you can go 30k miles more. But easier to just get it changed some time at or after 120k miles.

 

He’s afraid that your cat will be stolen before then and you will sell the car.

Stolen catalytic converter in london uk | PriusChat

 

But I wouldn't do it early just for the fun of it.
He wants the $$$$ now. He doesn't want to wait 6k miles/6months more.
He’s afraid that your cat will be stolen before then and you will sell the car.

You guys are feeling pretty frisky today....

 

It's that time. At the 120K service get them swapped out. The problem with older plugs is that the electrodes wear, and as the plug gets older the spark gap increases. At some point, this leads to a sufficiently weak spark that you see performance differences. I have yet to change a spark plug at the manufacturer's specified interval that had an in-spec gap.

As cheap as spark plugs are, and as easy as they are to replace, I typically change them earlier than recommended.

 

This sentence is oddly worded. It would make the most sense if you forgot the negative: "I have not noticed any significant problem in starting the car so far."

if you have noticed, starting issues, he is on the right track, (Symptoms of Bad or Failing Spark Plugs - Autoblog) if you have NOT noticed starting issues, the mechanic is just behind on his boat payments and want your money.

 

I typically would replace PCV valve ($3 item) during spark plug replacement since they are located in same general area. My mileage actually went down a little bit after recent replacement. Do not know the cause.