Can you provide a link to the help page you're referring to?

I have this, as shown in the attached image, and it has settings for both cache and when to compact. What else are you seeking?

Thank you! Your screen shot is the help page I found, but I have attached a shot of my own Preferences page; you can see that the first line of text, which appears clearly as buttons on your image, looks like a single line of text on mine, and I hadn't discovered the words were clickable - and of course every time I turned to the page they were showing the General options anyway!

What I really want to do is to stop Thunderbird asking me every few minutes if I want to compact my folders, but this may have got me a stage further...

They are tabs, but that is an unfortunate styling being applied. I'm sure it's all very modern and flat, but it does pander to design for touch screen usage and doesn't (IMHO) serve well regular point-and-click with a mouse.

I would urge you not to disable compacting. Users who put it off tend to have catastrophic data loss accidents if anything goes wrong.

My own approach is to file useful or important messages into their own folders, keeping the Inbox and Sent folders empty. Compacting is only relevant in folders where messages are frequently deleted, so if we move useful messages to their own folders, these storage folders will only rarely have deletions and so don't need to be compacted so often.

If you allow messages to accumulate in the Inbox, you have a constant churn of deleting unwanted messages whilst preserving those you do want to keep. That means compaction has more to do and so takes longer to run.

Many thanks. Your advice about compacting was much more helpful than the help pages' simple "Not recommended".