If you are requiring escrow then it should be set up and disclosed with the consummation of the loan with the initial analysis given at that time or within 45 days of establishing the escrow account.
In the one time closings I referenced above the escrow account was established at consummation and the initial analysis was based on when the first P&I payment came due. There was no escrow payments during the construction phase of the loan. The first escrow payment came due with the first scheduled P&I payment.
I know it's a personal preference but after working both with a single phase (1 closing) const/perm loan and a 2 phase (2 closings) const/perm loan, the 2 phase is much easier to deal with IMO. Especially if there are cost overruns and/or other modification needed during the construction phase.
I've not dealt with a single phase const/perm loan in over 10 years and I don't miss them at all.