RAF RC-135 conversions
Please look up some accurate facts, guys.
The three KCs being converted are in the last ten KC-135 built and NONE have been "stored" in the desert. The last KC is 64-14840.
The very last -135s are all RCs:
RC-135V: 64-14841 to14846 and 14848
RC-135U: 64-14847 and 14849.
14849 is the last -135 of any model.
All the RCs were originally RC-135Cs when initially built and began service flying around 1967, replacing the RB-47Hs in the SIGINT reconnaissance role.
The KC-135s have considerably less airframe hours than many RC-135s. The three RAF aircraft will be the low-time members of the Rivet Joint fleet as some of the RC-135Ws now have over 50,000 total airframe hours. (The -Ws were originally RC-135Ms and built up tremendous hours during the Vietnam war flying 18-hr COMBAT APPLE missions off the N Vietnam coast.)
None of this has anything to do with the viability of the airframe as modifications by Boeing (wing re-skins in the '70s and '80s) and L-3 (previously E-Systems and Raytheon) at Greenville have kept these jets in very good condition. Age of a modern airframe means very little, unless there is an original flaw which finally manifests itself. Given the size of the -135 fleet any such issue has surfaced already, unlike the Nimrod problems (given the small fleet and added systems problems - A/R).
If anything, the Nimrods displayed considerably more issues due to age of design and airframe than has the -135.