Can a notified CE (NCE) change duration once it has been added to the programme?
E.g. If NCE added in June with 10d duration, can it have changed to 20d duration by August programme submission? (still a notified CE only - no quote as yet received from Contractor)
Yes - as can any activity on the programme from period to period. If any activity is known to be wrong then it can (and should) be changed on the programme. This does not change entitlement within the CE quotation, as it should be based upon what would have been reasonable to have allowed for it at the time it was instructed/notified.
It also begs the question why you have not received a quote - as it is typically four weeks between programme submissions and the quote should be issued within three weeks. Indeed, if they have not submitted a quote within three weeks then the PM should (rather than could) make their own assessment - which would be what they believe to have been the correct forecast of that activity. That assessment may or may not be either of the duration’s that have been shown on the programme.