Hell roll the dice on a piston engine, automobiles run thousands of hours withought this warning. I would feel safe going with the manufacturers reccomendations. Play it on the safe side if said engine has a magnetic metal detector it will reveal the condition of the engine, nothing larger than a muddy consistancy of metal is normal wear, change the filter and keep on trucking. Other instruments such as your oil pressure guage are what you should monitor during your inflight D indication.