A comma is used before a subordinate clause that follows an independent clause--but only if the thoughts of the two clauses are not closely related. A change of subject from the independent clause to the subordinate clause is usally a clear indication that the thoughts of the two clauses are not closely related. (Rule from Eugene Ehrlich's "Punctuation, capitalization, and spelling book)
The city council will meet twice next week, when the bill for revision of the charter comes up for its final vote.
I will not take a long airplane flight, as long as you refuse to go along with me.
Should there be commas in the sentences above?
I'd definitely use one in the first. I think the second is optional.