Use of the adverb "then"?

Hi. Would you say the use of the adverb "then" for the following sentence type is limited to certain cases involving the subordinate clause makers (are they markers anyway??) like "once" and doesn't involve (include?) that of the marker (is that a marker?) "when?

eg,

1. Once you have finished your test, then you are to take a break.

2. When you think you can't do any more problems on the test, then it might be wise to check the answers to the questions you did before handing in the test.

3. If he didn't do the current assignment, then you shouldn't give him the next assignment.