On average we send between 10-35 email campaigns in a single day at least once a week, so I can definitely shed some light 🙂
Create a static list and add a step to the flow of each of your email campaigns that adds every lead that is sent one of your three email campaigns to that static list (i.e. "was sent email campaign Day/Month/Year") In the smart list in the smart campiagn for your 2 PM send, add a filter that says member of list NOT in your static list. This will ensure that any lead that was sent one of your other emails will not get the 2 PM send.
Then when you are ready to email these leads again later, use the same smart list that you used for the 2 Pm send, but just add a filter to your smart list that says member NOT in your static list, and the remainder will be the leads that received one of your original 3 emails and that you now want to send your other one.
Hope this helps!