I read through the links you provided and I'm unclear about one thing: do settings in
~/.profile override (or, at least, are they applied later than) settings in /etc/bash.bashrc? I have a feeling that I probably shouldn't really be editing things like HISTSIZE and HISTFILESIZE in the global file /etc/bash.bashrc, since that affects all users, not just me (even though in this case I am actually the only user of this particular computer).