I agree that only the author can answer whether there's any more story left to tell, but 14 is getting a bit long in the tooth. You say you've got good downloads, because at this point, the total number of volumes will likely intimidate any new readers, meaning you're basically preaching to the choir—writing for you existing fans, rather than reaching out to new fans and expanding your base.
It's a bit like those newbie writers who set out to write an opus, resulting in one story that goes on for more than 150 chapters. At some point, you need to sit back and think 'Where the fuck is this going?'. Too often, authors are mostly writing for themselves, and if they revised the work, they'd end up dumping a lot of the content as extraneous to the essential plot.
However, you're writing this for you. Like you, I started writing because I missed the types of story that publishers no longer are willing to publish, so I'm unconcerned with whether they sell or not, or whether I've got a large or niche following. I write for myself and my muses.
Since you're essentially retired, this is likely a form of therapy for you, so don't worry about the length. Yet, if you've got this much creative energy, you needn't spend it all on the same story. You could just as well have written another twelve stories which all reach additional readers. Just something to consider.