I know it might sound counter-intuitive but after dealing with other frustrating issues (unit colors not sticking after channel name change, google ads appearing everywhere) I'm considering having ONE channel per site with all units being assigned to that single channel.
I don't need the channel data for optimizing because I have the same template on a site that I use for testing and only that site would retain individual channels. I would use that sites data to implement changes on other sites.
I don't have placement targeting on but I have seen in adwords that if multiple unit types are lumped into one channel then Google displays the different unit types available to that channel, so placement targeting is a non-issue.
Should i expect any negative impact if I go and make channel changes to units that have been untouched for years? Is unit history playing a role in my earnings?