It won't wear the trigger block , if it's a flat race ie three piece , they are designed so one piece stays still, it's the whole point of a thrust race.
As others have said the longevity of needle bearings would be my concern and I would feel a lot more confident using a plain bearing.
Delrin or Iglidur have low efficients of friction and should stand up pretty well.
I experimented with thrust bearings about 8 or so years ago.
I never really noticed an improvement over my usual setups.
If anything, as Nick says above, they pinch crucial spring room, so I stopped using them.
B.A.S.C. member