It is tempting to say it /never/ ends cleanly, but honestly it is more like 9 times out of 10.
My environment: Windows-XP in a public library. PAC on a USB stick. Thunderbird P.E. 45.1.1. Network painfully slow.
When I get a 10-minute warning that my time is running out, I shutdown all my apps. Thunderbird appears to go away.
Then, after waiting a few minutes, I try to exit the PA Platform. It cogitates for quite a while. then tells me that T-bird is still running.
Usually, I tell it to try again. Eventually the Mozilla Crash Reporter informs me that Thunderbird has crashed.
When I dismiss that, I can safely exit PA and reclaim my stick. Usually.
I'd wager you're using a slower drive on a slower computer. Unfortunately, there's not a lot you can do to speed things up in that case. I'm not sure why Thunderbird is busily doing things unless you lots of email on your drive. Is that the case?
Sometimes, the impossible can become possible, if you're awesome!
It's a USB, I don't have any speed specs. The computer, not sure; Public Library, and locked down by folk who know how. Network is also quite slow.
I have two IMAP accounts -- I would need a different medium to actually download the mail.
Yes, it is painfully slow. But more than 10-minutes to exit? Should I expect it to exit cleanly if I give it more time?
Anyway, thanks John.