That is probably average trail use for an XJ. Coil overs are really not necessary for that. Save the money. Coil springs work well whether they are on shocks (coil overs) or mounted to the frame. Here is the thing that most people don't know about them. The coil overs work well off road because of the very soft spring rate combined with lots of shock. But they don't corner worth a hoot. So they are generally not very streetable unless they are set up for it, then they don't work well off road. The best you can do for all around is get reservoir shocks. But beware, you need to get rebuildable shocks and plan on revalving them. Those are considered racing shocks and are stiff on the compression and rebound and you need to soften them up on the compression stroke to be able to live with them. And Fox is notorious for that. So how long is a long trail run and at what speed?