A customer portfolio isn’t something you achieve once and than gets static, regardless how important are your customers (or for that same reason – they became too important making you too vulnerable if one day they decide to walk away).
Don’t take anything for granted, not in life and surely not in business.
Therefore building and maintaining a customer pipeline is a crucial exercise and ongoing exercise, just as important as managing your existent portfolio.
Based on my own field experience in different corporations (sizes, markets and industry segments) I’ve build up my own reference document that reflects crucial steps and approached in order to get the most out of that exercise and not only a “tick in the box” exercise to please your line manager or system.