I think the question you are asking is..
How many accounts per "Client"?
not project..
Typically you'd create a set of Google accounts to suit your niche and client.
our Artificial Intelligence Profiles is the best place to get these accounts created. see my special offer link here
www.peterdrew.aiprofiles.com
Using the link above you can get custom created google accounts to suit your niche/client etc. these work very well and stick around forever.. we mimic making accounts just like a human does , thus they never get pulled for any spam penalties etc.
Then typically I have some test accounts, that everything goes through first to test the waters etc. And also purely used for link building only etc.
Other accounts I use for projects that are all mixed in together.. but a rule of thumb is new accounts for individual clients..
cheers