Thank you, @SRF10. I added those details in OP.
If I come back to the forum after months, I don't see why do I have to change my password, if I don't lose it.
Even if there's strange activity on your account while you were away? What will be your first step if the person that used your account, didn't change anything?

Of course, I will change my password if I find out strange activities with my account (log-in IP, and strange PMs in my Outbox).
For one who don't know how to check your log-in IPs (for the last 30 days), visit that page after logging in your account:
https://bitcointalk.org/myips.phpMake sure you choose the option: Limit your IP retentionn (Profile --- Account Related Settings --- Choose that option)
It's tricky to get email notifications right so that they're not too spammy. Maybe later.
For now, I added this page where you can see your IP logs for the past 30 days:
https://bitcointalk.org/myips.php . You could pretty easily write a userscript to periodically check this and warn you if it's weird. (But don't scrape it on every pageload.)
I don't want to make older IP logs automatically accessible because that'd give a hacker a bunch of useful/sensitive information. But 30 days is probably not too harmful.