If you want to take your stone-maintenance up a notch, get yourself an atoma diamond plate. Over time, regular truing stones can wear down or warp slightly. This guy will never have those issues. The stainless steel plate will stay perfectly flat forever, and the replaceable diamond surface wears far more slowly than a regular stone.
The diamond grit rips through wonky stones, making them flat as a pancake. When it wears down, you can simply peel it off, purchase a replacement, and stick it on with the built-in adhesive. This flattening plate can leave your stones a little rough, so grab a nagura stone to smooth them out afterwards.