Three things that all businesses do: Shift - acquire customers and bring them to your brand; Lift - improve the value of existing customers; Retain - maintain a healthy portfolio of top performing customers.
You should be measuring all three - pipeline velocity is the speed at which you are generating revenues, customer velocity is the speed that you are acquiring customers, retention is the rate at which you are keeping customers.
The caveat to all of this is that retaining a $10000 customer is better than retaining a $10 customer. Acquiring a $10000 customer is better than acquiring a $10 customer. Managing your portfolio will help you determine marketing and sales goals and initiatives.