mind or minds (continued)

[joham]

1. Could I draw a conclusion from the answers to my last post that "make up our mind"="make up our minds"?
2. I searched the web at dictionary.com and got the number of results as follows:
change their mind 39 400
change their minds 66 000
changed their mind 18 500
changed their minds 36 200
But in dictionaries we can only read sentences with "change(d) their/our minds". Is the singular of mind in this phrase nearly as good as the plural?

And how about:
to our mind/minds?
speak our mind/minds?
go/be out of their mind/minds?
You've been on our mind/minds?
take our mind/minds off sth?
to our mind/minds?
Forgive me for raising so many questions. We Chinese learners find it a headache to deal with such questions and Dictionaries seem not to offer us such answers.

[Anglika]

It will have to come down to whether you are talking about an individual's mind, a collective mind or multiple minds.

Which it is likely to be will generally be assumed from the context.

If somebody cannot make up their mind....

If the voters cannot make up their minds...

If the electorate cannot make up their minds/mind/its mind = there are various options here with a collective noun governing it.

My advice would be to consider your logic in your own writing, and not worry too much about what others have done.