Shocks start to lose fluid past the bushing from the day they are put into use. A small amount of fluid discovered past the bushing is no cause for alarm. On the other hand, if the shock is making noise, or no longer dampens the motion of the wheel and tire, it is time for a quality replacement. Ford offers a specific shock for each of the tire combinations it offers. No mono-tube shock such as the Bilstein is offered for the Edge. At 140,000 miles my shocks and struts are still going strong.
Spraying oil outside a shock is a traditional form of deception used by dishonest service stations.