Unlike most other animals, the skin of a snake does not change in size. Therefore in order to grow, the snake must shed its skin. This happens multiple times during the life of a snake. The process is a natural part of its maturity.
Founding teams are often similar. If the members of the founding team are unable to grow, over time they need to be shed. This should be as natural a maturing process as a snake loosing its skin, and need not be an emotional parting. Founders who become overly attached to their initial teams often end up with teams constricting the growth of the organization.
During the startup phase, founders are prone to attract less experienced executives often based upon a pre-existing personal relationship. Letting this relationship color their assessment can derail even the best entrepreneur. Maintaining an objective view of team members is critical to a founder intending to maintain her tenure. Should the founder be unable to objectively assess her team, it is likely that her successor will. Unfortunately, terminations at the hands of a successor tend to be emotionally charged and traumatic for the organization.