<quote>But--what about the case of, "I must have this job completed by tomorrow afternoon--bosses' orders"?
</quote]

Possibly there might be a tendency to avoid "have to have", but if we think of the two sentences:

I must finish this by tomorrow afternoon -- boss's orders
I have to finish this by tomorrow afternoon -- boss's orders

it seems to me that I'm taking more responsibility for the situation than in the second. As a teenager, which would you have been more likely to say:

I have to be home by 10
I must be home by 10.

I think the first one is more likely to arise from a parent-imposed curfew while the second is more likely to be continued 'because I want to watch Star Trek'.

Bingley

Bingley