Dave, What I’m going to say is probably considered heresy by many, but it is what I whole heartedly believe at this time. Maybe I’ll learn better in the future. But the following is my experience after baking hundreds of SFSD breads.
Carl’s Oregon Trail starter ceased to be a few weeks after you got it home and started feeding it with your flour in your environment. The same will occur with any starter to keep and maintain.
Sour flavored sourdough dough is not nearly as dependent on the starter as many bakers believe.
This is where the real heresy begins. I believe the sour flavor is mostly produced during the actual fermentation of the dough. Starters do have some affect for sure. A NMNF that is aged and composed of 100% rye is a great example, but even a properly fermented and aged NMNF starter needs time during dough fermentation to multiply the bacteria.