as a general rule, on high hour (>9000 hrs)trucks with an e-27 code, I look at it about like a long due tune up, and while I do eyeball the wires and connections to the POS and PHASE (Crankshaft and Camshaft position sensors) I tell the customer to expect to replace all the coil packs and spark plugs.
As Kevin_t notes, using the correct plugs, and correct gap, not assuming the gap is correct, makes a world of difference in these trucks, and you won't be looking at the next e-27 for a few years (or until the fan draws up a plastic bag and wipes the POS wires to a frayed mess).