The problem here is that Boehner isn't really just waxing philosophical about stepping down. He's
threatening to, believing that it will strengthen his position as Speaker.
The guy looks in the mirror every day and sees someone he believes is completely indispensable to holding the GOP Caucus together, and assumes everyone else (at least in the GOP caucus) knows it. This probably has more to do with Boehner pushing the caucus towards immigration reform than any alleged "health issues" he may/may not be having.
IOW, what we're seeing is him trying to pull this: