Yep, logging in to Backblaze is a PITA, in addition to their unreasonably short-lived sessions.
They're not 'short-ish', they're shorter than... every actual 'session' I have with the site.
They're so short that I've been checking cookies and wondering what I'm blocking that's breaking it until I saw other comments here.
There doesn't seem much utility to me in having the website session expire before the screen locks - apart from anything else the computer quite likely has B2 keys or the consumer app installed if it had the website logged in.
Perhaps there's some other threat I'm missing?