I think this is a must, 5 is just never going to cut. I think a maximum to sit around 10-15 would be a welcome addition to us all.
The math states that relations = the number of interactions / a period of time.
That number of interactions is, at the minimum, 7 before trust and authority are established.
Adding “manual” emails to the sequences is not a solve… you can’t build a repeatable process and know if it’s working when you manually are adjusting it with each send. I don’t mean adjusting the copy but adjusting the frequency. Or is my assumption incorrect on the process you are referring to @glencornell ?