thanks very much for your responses. the truck is an SSV owned by a local (Texas) fire department. I've got a 34 page carfax that came with it. it does not list every single detail, but I'm going to assume routine maintenance was done, such as brakes, etc., at or better than OEM intervals. I know there's a lot of discussion about Ford's intervals, but that's my working assumption until l see a reason not to believe it.
For example, before I bought it, I took it to my mechanic and had it inspected. the parking brake passed, the rear rotor did not. I'm not going to replace just one side, though I'm willing to do just one axle at a time.
I've read about more than one example of a stuck rotor. If i run into any significant trouble, I'm just going to button it back up and take it to my mechanic. I do have access to a fully equipped shop and considerable technical assistance - I'm retired military and the local base has a very well equipped auto shop. so if that won't take care of it, I'm turning it over to the pros.
i did a lot of research before I posted here; much to my surprise, slotted and drilled rotors were not necessarily the ultimate solution; and the arguments made for a good solid rotor in everyday driving and light towing made sense. One reason for asking about rotors here was to make sure I didn't miss something. This is my first Expedition; a well reasoned theoretical argument about brake rotors is a general case; not a specific one. I wanted to make sure the Expedition didn't turn out to be an exception and I should actually be using something else.
So, based on your responses, I'm going with the solid rotor and ceramic pads, at the best price I can get for quality brands.
thanks very much, guys.