On a 7000km trip, with those twin filters, I would take no spares, just remove and tap them clean at about halfway through your journey.
What I would do BEFORE the trip, is to either seal them in with grease around the edge, or even silicone them down. The silicone option means you having to take a tube along for re-sealing after halfway cleaning.
Make SURE no dust can get past the foam edges of that paper-element.