A long password doesn't mean much by itself. If it has been previously leaked in a different breach, reused, is relatively easily brute-forced - then yes, you need to worry about that.

The bigger problem is: even if you are safe right now, your vault is out there. If at any point your master password surfaces somewhere - all your accounts are instantly compromised. So the only sensible solution IMO is to start rotating all passwords and usernames today.