If your top three clients account for more than half your revenue, your business is structurally fragile. Lose one and cash flow collapses. It also destroys business value — buyers and lenders discount heavily for concentration risk, and if you die with key relationships sitting in your head rather than your systems, the asset your family inherits may be worth a fraction of what it was on paper.
The fix is not to fire your best clients — it is to grow the rest. Measure concentration quarterly. Set a ceiling (e.g. no single client above 15%). Introduce other team members into key relationships so they survive without you. Move informal arrangements to formal contracts with notice periods. Build recurring revenue. And document everything in a CRM that others can access.
If your biggest client leaving tomorrow would put the business in serious trouble, that is not just a risk — it is the risk. It deserves the same attention as every other part of your estate plan.