The fewer the firms you retain, the more you need to intervene in their personnel management decisions
One of the consequences of convergence, when a handful of firms take on a large portion of your work, is that you probably should engage yourself more in their issues of “bench strength,” succession planning, training, evaluations, promotions, and relationship partners – to name a management decisions of law firms. This heightened involvement follows from the responsibility now vested in those primary firms; you need to protect your investment in knowledge capital.
Grafting a few firms onto your tree brings shade and fruit but also requires more pruning and care (See my post of Feb. 16, 2008: convergence with 26 references.).