If, you are asking how to transition from founding members to non-founding members, the answer is over time. It is worth keeping a few of the original board members on to transition some of the knowledge and values. Of course, those holdovers are going to have to be open to the changes that are inevitable with any changing of the guard. A concept that is easier in theory than in practice.
One of the most important aspects of a successful transition is the transfer of contacts. An updated database is not enough. The database will give the basic information, but in order for the relationships to be transferred, a good deal of personal introductions will be necessary. To stay on board, donors, volunteers, associates, businesses and foundations need to understand the need for the transition and share the confidence of the old guard in the new leaders who will assume the responsibilities of the helm. And anything short of the respect these stakeholders deserve will deem their previous relationship with the organization as irrelevant to the future.
The costs of retaining a funder, donor or volunteer are always drastically less than finding a new one. Mistreating these key contacts would be a mistake on many fronts.
If, on the other hand, it is too late for an orderly transition there is a mountain for the new team to climb. And I know this from experience.
Calls must be placed and meetings should be arranged to establish new relationships with the above-mentioned donors, volunteers, associates, businesses and foundations. Of course, while an introduction from the former contact manager makes things easier and often more successful, every attempt to retain the connection is important.
Remember—the costs of retaining a donor are always less than obtaining a new one.
Realisitically, some relationships will not be retained because a new team will take on a new view. Some will like this new look and some will not. But a new perspective and new energy can help an organization advance to a higher level of effectiveness. Stagnation is not healthy for any organization so accept the positives and work to minimize the negatives of the changes and push forward.