OK, so I am in the process of converting my home-brew setting over from AD&D 2nd to Pathfinder. I (personally) prefer playing and DMing at the "low" and "heroic" levels, and looking over my 10 year old notes the setting reflects this - traditionally, campaigns have petered out around 12th/13th level and the surviving characters have been retired to run temples/gilds/small countries (many of them have entered the canon as minor NPCs...)
Then it hit me: rather than end campaigns when the characters progress beyond the levels I enjoy running, why not cap advancement at 12th level and allow mythic characters - beyond 12th, the party would use XP to learn new feats (as per any of the EX systems) and adventuring could focus on gaining new mythic tiers.
So, my question is should I try and do this? Is combining the mythic rules with EX advancement a good idea (or even possible?!)