The research is available at the National Center for Charitable Statistics. You can also find information on the life cycle of a private foundation and other nonprofits on the Internal Revenue Service website.
The Center for Philanthropy merged with The Fundraising School at University of Indiana and they have some statistics about raising money. According to contributors to the literature long sponsored by The Fundraising School, it takes between 18 and 36 months to develop a major donor. I don't know how much is available without participating in a workshop or purchasing the information, but the Center would be a prime spot for such information.
You can also go online and search for the Evergreen Society. Putnam Barber, now a Sr. Researcher for Idealist.org, was once the President of the Evergreen Society and had a really informative web site around nonprofit business.
I don't know if the CharityChannel has direct information related to what you're seeking, but they are also a good site to check out.
