It could have merit.
Consider - We have night tennis, night golf and a host of other nighttime activities that have proven successful. So why couldn't the org arrange for a nightshift of witlessing? Those people that are recorded as NAHs during the day, would surely be at home in the evening, and, the later the brothers called, the better chance they would have of finding someone at home.
I'm sure there would be many honest hearted individuals who would welcome being woken at 3 a.m. for a solid discussion of fable principles at their front door. Could be more opportunities to be invited in - maybe the householder could retire back to bed and a good bedside chat could develop. How up close and personal that experience could be.
Waiting for people leaving the theatre or cinemas at midnight is another example of potential field activity, along with waiting for employees finishing their own nightshift at 6 a.m. Time enough then for those dedicated brothers to freshen up after brekkie at Maccas and to be ready for the field group at 9 a.m. Think of the experiences that could be related before the text being discussed.
cheeses - who is lamenting the fact that there wasn't night field work in his time.