RE: 100% Carbon gear
Since you already have the sails, then the mast and boom upgrades (at the right price it sounds like) make good sense.
As far a durability, the Diablo's have no scrim, or X-ply so they will be degrading (all sails do, even those with scrim and X-py) from UV exposure.
Best thing you can do is to get a cover for your sails and keep them either covered from UV, in the shade somewhere where there is no UV exposure, or on the water being sailed.
Don't leave your rigged sails lying on the beach in the sun any more than you absolutely have to.
This will give you the best long term reliability.
As far as the masts and boom, a coat of good car wax (carnuba type) or a coating with McLube Sail-Kote or Elmer's "Slide-All" will help to keep them looking good, help to make them "slide" into to the luff sleeve with less effort. DO NOT coat or wax the area where your boom clamps!!!!!!!!
As far as keeping your new (older) boom working well, get a hot water hose, remove the tail piece from the head and boom tubes, then rinse out the inside of the boom tubes thoroughly, rinse off the extension tubes, and rub a bar of soap over the extension tubes while they are still wet. Rub some soap on your finger and put some soap down inside the boom tubes.
When you slide it back together I think you will like the smooth way the boom slides for adjustment.
That's about the best you can do to improve the longevity of your sails masts and boom.
Hope this helps,