Tolkien states in Appendix A that Aragorn and Eomer fought many battles together in the North East and South East until Eomer was too old to ride. So that is like 30-40 more years of war with just Rhun and Harad.
Tolkien also states somewhere (probably the end of book six) that Aragorn spent pretty much all of his time as King reclaiming lands that once belonged to Gondor and Arnor. That is a lot of land, so that means even more wars with the inhabitants, as they are not just going to give it up.
It should make for a smashing good campaign.