Hi KateRua
You could try using the retention level option to bpimagelist. So (assuming you have the default retention level settings where rl=6 for 6 months - try this command:
# bpimagelist -hoursago 4400 -rl 6
4400 hours is approximately 6 months (there would be no need to search back further). If you need the output in more readable format try using the "-L" or "-U" options. If your retention level settings are not standard, then use the bpretlevel command to see what retention level(s) correspond to 6 ,months.
Cheers
David