If you do ANY off-roading, leave the locker in !--
I've been running WELDED front and rear diffs for over 10 years and sure there will be some extra rear tire wear-- lets say you get 20k miles on a set of tires, you would see @18k on the rears without rotateing tires. YES it chirps-- one rear tire is slipping-- but with the weight of a pick up rear end--- wear is ALMOST a '0' factor.
I share the 'daily driver' duties between my '92 stock toy, and my '85 rock- crawlin toy--
local 4X runs i drive to in the modified '85, (even the 7 hour drive to the Rubicon, the 5 hour drive to Beatty , Nevada== to act as vehicle rescue at Cal-Roc event,) On LONG trips or for week end trips, the '85- welded diffs, and all-- is flat towed.
you will not loose 'u' joints or other things due to a locker run on the street.
it is no big thing to change out a third member--- as long as you use the same gear ratio as you have in the front ! To change out a rear diff will take about 30-40 min.