The key is to stay focused on creating a great culture in your firm to attract and retain the very best people. Build a great team that provides superior services to your clients and your chances of losing a client (let along a good staff person) go down significantly.
Sadly, there are still a lot of firms focused on trying to stop undesirable behavior rather than stimulating desirable outcomes. It's the difference between the abundance versus scarcity mindset. The scarcity mindset continues to be driven by out-dated partner comp and buy-out models.
Just as you can't control when and how a client exits a firm, firms of the future will not be putting the retirement burden of one generation onto the next. I added a reply post to Jason's and he came back to me with "You are awesome" to that I replied . . . "Not awesome, just cranky." I am weary of partners who hoard work to keep their book of business full so they look good in partner meetings and can get a bigger buy out in the end (assuming anyone wants to follow in their footsteps). In the process of protecting their "book", these same partners limit the growth of those around them (thereby putting succession at risk) AND they rob their clients of the brain trust that forms when you build client service teams.
Frankly, a partner who refers to clients as his or hers is the last person that deserves them. Likewise, firms that refer to clients as theirs (in an ownership sense) also run the risk of putting their focus on the wrong things. Just because I have taken my business to a particular company in the past is no guarantee I will be theirs in the future. We talk so much about client loyalty when, in fact, the real power in the relation ship depends on firm loyalty to client needs.
As Maister would say, "Love your clients to death." Blumer says, "Service the crap out of them." I would say, "Advocate for your clients' success, do whatever it takes to support their dreams, and your loyalty to them will be returned in kind."
Ultimately, Clients vote with their feet and employees vote with their passion! If we work it right, our clients' feet, our employees' passion, and our firms are all heading in the same direction. If it turns out they are not, the firm has only itself to blame for essentially making the choice to non-compete (not doing what it takes) to keep customers and employees truly happy.