Really as BRX says. I hate rounds on fretless anyway but I did buy an ESP fretless recently strung with rounds. Had clearly been tried in a few hands, even though it's new, and the strings had marked the board. You can sand a board with the right radius sanding block if you want rounds. Anyway I like a darker tone so I use halfwounds (Status Hotwires). Less finger noise and much, much less damage to the board.
Sanding/planing the board will alter the action, as a refret probably would too. But if you are having your bass setup every so often these things can all be looked at at the same time. Don't think oil would protect the board much.
Really down to personal taste.