If it ain't broke/braking don't fix it. That being said, after a couple years of annual services you might have dartanium washers degrade or become more brittle. The carbontex option is a cheap alternative for better strength and drag power, I can't comment on the drag because I don't really tighten my drags. From what I've read from other reviews for Carbontex is they are more powerful, don't know how much more powerful (pound vs pound comparison) but I will have to take their word for it.
I replaced dartaniums out of one 51e because I had a grip issue with it tearing down a reel, now I know I have hand problems but the washer was weaker than the others, it needed to be replaced and te carbontex was a cheap easy option.
Now was it worth switching all of them out after I tried one, not really. In time when there is play money not ready to be spent ill outfit all my other reels with them for a longer lasting washer.