If you're happy with the way the bass sounds, I wouldn't put any coating on it. True, roundwounds (and all strings) will wear on the board, but they are very thick and can handle many resurfacings before needing replacing. Currently, a fretless fingerboard replacement (without LEDs) runs $450-550.
Of course, anything that isn't harder than the strings will wear, and things that are harder than the strings will wear the strings.
We just made a new fretless Orion bass for Trip (he has that big 8-string Ocean Blue in the Featured Custom archive) with our hard polyester finish in the fingerboard. He's only had it for about a week, but I'll ask him how it's wearing and how the sound is different to his ears.