When to replace spark plugs?

[cheapo]

I have the service schedule for my car (https://www.customers.volvocars.com/owners/docs/2003/2003_maintenance_charts/2003_maintenance.html). It tells me the spark plugs are due for replacement at 192,000 km. We bought the car at about 197k and the service records I received from the previous owner don't show the plugs being done in the two years he owned it. The car is now due for its 228k service.

Are spark plugs one of those items that reward following the maintenance schedule or can I leave them be?

[acools]

EVeryone has opinion about maintenance, some follow the recommended schedule and some use sandpaper and electrical tape to extend the life.

My choice? Every 30k miles or 50k km my car gets fresh plugs, they are cheap and ensure I have a strong spark.

Andres

[Astro14]

+1 on what Andres said. Besides, taking a peek at the plug condition allows you insight into the combustion chamber, and alerts you to potential problems...

[Willy]

I also have replaced the spark plugs after about 50KKm (took me 8 years to get there :p).
They were still within service limits, Volvo's maintenance schedule says 96KKm!
However, it seems as if the engine runs smoother with the new spark plugs.
I used OEM spark plugs, I didn't find them to be cheap (65€ or more than 90$)
Willy

[skibo]

My XC started to miss during acceleration at around 85,000 miles ( 136,000 km ). A new set of OEM plugs fixed it.

[95SE]

does inspecting spark plugs necessitate the disconnecting of the battery? I know many electrical items or any for that matter cannot be unplugged without first disconnecting the battery that is why I ask.

[BillAileo]

There is no need to disconnect the battery. FWIW: disconnecting a Volvo's battery should not be done without first carefully reading the steps necessary to do it.