Smart Send Time — When to use Exploratory vs. Focused

Hi @notsamharper,

Welcome to the Community.

Thanks for sharing your question regarding Smart Send Times. 
As you know already from optimizing your send time, Smart Sending time gathers data on how emails perform based on the time the email is sent (not the type of day it is sent). In this specific case, one exploratory send would be enough to determine when is the best time to send emails. Having said that, the more tests you run the more accurate the data will be. You can also run a a focused send after the initial exploratory send to further narrow down the optimal send time. However, if you had found your optimal send time through testing then you should be good to go! When it comes to the Exploratory Smart Send feature, we actually will send an equal amount of emails over the span of 24 hours without excluding any hours. 

I hope this helps clear some things up! If you're looking for some more information I would recommend taking a look at these docs: 
Getting Started with Smart Send Time
Understand Smart Send Time Results

Thanks!
Alex