I was looking at my rear leafs and they seem arched correctly over the axle but go up then arch back down slightly near each end. I though it was maybe sagging but when measured I still have 17" from center of wheel to bottom of factory flare. Would this be normal or are they nearing time to be replaced? It is an 85 xj with 142K miles on it.

That's normal wear- and they are worn. They take on almost an "S" shape, the ends near the shackles/mounts do most of the work and wear out first, bending slightly backwards. It's harmless, the fix is new springs. Mine have been like that a long time. (I don't tow anything and don't want to mess with those bolts, lol)