Cement is timing issue; you want to pour it just about when you've mixed it.

Entirely competent people faced with relining drains might well elect to say "I think we'll have the relining done for eleven, but let's wait until it is done to queue up the cement, because we so do not want to go an hour over, that gets awkward" (though more so in the summer); this lot appear to be operating on a "it doesn't get awkward, it doesn't dare" schedule, which -- at least if you see the neat new patch of cement when they said they would be done! -- is an excellent good sign.