Having the timing belt, idlers & tensioners, and water pump replaced on '98 Avalon with about 110k miles. The conventional wisdom I've heard on replacing the cam seal is inspect and replace if it's leaking. Is this correct? What's the danger if it begins to leak later? Is there any wisdom in just doing it along with the Timing belt, etc. Shop said it would be an additional 2 hrs of labor to do. Any input would be much appreciated.