not sure what’s best here… playing around with:

# don't put duplicate lines in the history. See bash(1) for more options
# ... or force ignoredups and ignorespace
HISTCONTROL=ignoredups:ignorespace

# append to the history file, don't overwrite it
shopt -s histappend

#HISTFILE=$HOME/.bash/history/$$

# for setting history length see HISTSIZE and HISTFILESIZE in bash(1)
HISTSIZE=1000
HISTFILESIZE=2000

PROMPT_COMMAND="history -a; history -n"
#PROMPT_COMMAND="history -a $HISTFILE ; history -n"

or

unset INPUTRC
export EDITOR=vi
export HISTSIZE=10000000
export HISTFILESIZE=10000000
export HISTTIMEFORAMT="%c"
export PROMPT_COMMAND='history -a && history -c && history -r'
set -o vi