You might want to try to figure out what you (or the previous owner) were doing to cause the wear. Typically it's caused by technique, not the strings IME.
I've yet to have a wear problem on a fretless and I've used rounds on just about everything. Most of the wear I've seen on other fretlesses seems to be caused by bending the strings instead of using a vibrato parallel to the strings. Very easy to avoid... don't do it. After all, you can rub a groove in a board bending flatwounds. Next stop... no strings?
IME Elixirs do not sound like bare roundwounds. That's why I've never used them, I get the exact sound I want with Nickel rounds and know how not to cause wear so there's no need to compromise. At the worst, if you had to have the board dressed every four or five years that's a small price to pay. I've only had one board dressed in several years of fretless ownership and that was on a brand new Carvin.
I set my basses up pretty low and use a light touch a la Willis.