When you install Iridium spark plugs instead of conventional spark plugs the Iridium spark plugs can last as long as 120,000 to 150,000 miles before you need to change them.
With conventional spark plugs you usually need to change those every 30,000 to 50,000 miles but with the Iridium spark plugs they can go longer.
Iridium spark plugs cost a bit more than regular spark plugs but they can be worth the extra cost to buy and install especially for vehicles that have hard to reach spark plugs.
I installed Iridium spark plugs in a van that was hard to reach the spark plugs so I did not need to change them as often.
But on my other vehicles where the spark plugs are easy to change I just use regular Autolite spark plugs which have served me well for over 50,000 miles.