Iron Man, Captain America and Thor aren't even hitting 11 or 12 years IF they are killed or written out in Endgame. Wolverine can appear in 7 to 8 movies (counting cross overs / cameos) within the neXt ten years but beyond that would be eXcessive. There are so many characters that can carry the X-Men. They can feature a dozen of them in every film without Wolverine. With the right material, Cyclops, Storm, Rogue, Jean, Gambit, Beast, Psylocke, Angel, Iceman, Colossus, Shadowcat and Nightcrawler can be as popular as the Wolverine. Then there's also Emma, Havok, Jubilee, Polaris, Bishop, Forge, Dazzler (to name a few) that can be featured in supporting roles. They are set for a dozen films even if the Wolverine only appears for 2 to 3 X-Men films.