Will they settle? If they will, how long might it take?

 

That depends on the condition of the donor springs. If they are well broken in, they will not sag after installing on your rig. This is what I experienced. I used well broken in donor leafs, (from another Cherokee) and the lift achieved has not sagged a bit. That was over a year and 15000 hard miles ago.

 

i run leafs off of a 1997 f-150 and they have not sagged in the year that i have had them on my jeep

 

Used s10 pack out of JY and after 3 yrs and 2 different rigs, it hasnt sagged any

 

ALL springs settle and sag. That said since B-packs are generally made from pre-sagged (used) springs they don't settle or sag as much as new springs or AALs. B-pack is technically a AAL system. Really comes down to where the Doners are from. If they are from a big truck like a F150, probably never, course they are also probably hard as running train rails. But if they are from a rig closer in weight, they will sag a little over time. If the donors were from another XJ or other Jeep then they will sag at the same rate that XJ springs sag.