Regularity in whelping time?

just a quick question as my mentor is away on her hols! my sibe is 62 days today, she is, i think in the early stages of labour. her first litter a year ago was bang on 63 days and she started delivering at 5.03 pm with last pup delivered at 11.52pm (i kept records of each pups delivery time and weight as advisd) my question is is she likely to begin giving birth at around the same time with this litter? my friends springer which has had 3 litters has always started at around 6.30 pm so wondered if this is a normal thing for dogs to do or if that was just coincidence? i have my bed set up downstairs and vets on standby just incase of any problems. will be able to contact my mentor in a few hours but unfortunatly she is in another country atm and its middle of the night! hence why iv asked on her. please note im not a byb im a trainee so to speak, my dog and stud dog are both hip scored and proven working parents with full 5 gen pedigree befor anyone starts with the whle byb an spaying lecture! thanks in advance for answers, i appreciate your views