Does anyone have a rough guess as to what mileage it's a good idea to change the cam phasers and/or the oil control valves on a high mileage Grand Caravan w/ a 3.6L?

 

don't touch it unless it ailed !!!! if you have knocking - thats just lifters/rocker arms .....if you catch it early .....no need to replace camshafts .....if you do need to replace camshaft(s) ...still no need to replace phasers .....unless they have failed ....