I had a flat black bumper on a Montero years ago. I just hit it with a rattle can once every year or tow, or whenever someone ran into the back of it.
IMHO cheap and easy touch up is undervalued.
But yes, for something you step on regularly I'd find a powder coater. FWIW, there are DIYs for powder coating that don't look too bad at this point. I've not tried any, YMMV.
'99 EB ex ENG KSWB news van, low rent 4x4 conversion (mostly fixed by now), home built interior.