While harder frets might last a little longer, there's the possible other result that they might make you change strings more frequently. Of course, this would depend on whether you change the strings when they don't sound good, or wait until they break (or rust) like some of us do.

All the threads we've had debating bone vs plastic vs tortoise bridges and nuts would suggest that you could get some tonal effects as well. An experiment I did with aluminum nuts on a lap dulcimer didn't turn out too well, because it made an open string sound a lot different than a fretted one.

I seem to recall that Luthiers Mercantile offered a couple of "special composition" fret wires, including a "super hard" one or two, a few years back; but a quick look at their site recently didn't find anything other than standard hardness. They, and others, do offer some variety in crown widths and heights. Perhaps a wider crown would give you a little slower wear. Depending on how fussy you are, though, changing the fret width or crown radius can affect the note-to-note intonation.

John