We have a timing info in our book. ->
https://www.amazon.com/Practical-Oracle-Business-Suite-Implementation/dp/1484214234 Exactly -> In section "EBS Upgrade Timing Summary"
The biggest effort of the work is spent on Database upgrade and installation of pre and main 12.2 upgrade driver phases. For instance we spent almost 7 hours for the upgrade driver..
It depends on your computational resources as well.. So I suggest you to make a demo on your TEST env first.. During the temo record your timing info for all the phases and then make a decision for PROD.