Following the chain of links and answers and explanations, we come to the conf file that says in the comments that it commonly results in two (2) kernels being saved, but can sometimes results in three (3) being saved.
IOW, it does automatically remove old kernels, it just keeps the last 2-3.
IOW, it does automatically remove old kernels, it just keeps the last 2-3.
So, yes, run "apt-get autoremove", that's it.