I agree with Sonic, I had my plugs wires, intake manifold gaskets and valve cover gaskets changed at 75,000 miles. I did this mainly because I had a problem with the truck sputtering and losing power when pulling out from a stop. I chased the problem for 6 months and finally i took it to my mechanic for diagnosis. It took him several hours to finally figure out that one of the spark plug connections on the coil was shorting out. So, a $60 dollar part cost me $250.
Therefore, like Sonic says, replace the coil with the plugs and wires or sooner.